REESE  LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 

Class 


The  D.  Van  Nostrand  Company 

intend  this  booK  to  be  sold  to  the  Public 
at  the  advertised  price,  and  supply  it  to 
the  Trade  on  terms  which  will  not  allow 
of  discount. 


WIRELESS  TELEGRAPHY; 


ITS   ORIGINS,  DEVELOPMENT,  INVENTIONS, 
AND   APPARATUS 


BY 

CHARLES   HENRY  SEWALL 

»/ 

AUTHOR  OF  "  PATENTED  TELEPHONY,"  "  THE  FUTURE  OF  LONG-DISTANCB 
COMMUNICATION  " 


WITH  85  DIAGRAMS  AND   ILLUSTRATIONS 


SECOND  EDITION  CORRECTED. 


NEW    YORK 
D.  VAN    NOSTRAND   COMPANY 

23  MURRAY  AND  27  WARREN  STS. 
1904 


WIRELESS  TELEGRAPHY; 


ITS   ORIGINS,  DEVELOPMENT,  INVENTIONS, 
AND   APPARATUS 


BY 

CHARLES   HENRY  SEWALL 

»7 

AUTHOR  OF  "  PATENTED  TELEPHONY,"  "  THE  FUTURE  OF  LONG-DISTANCE 
COMMUNICATION  " 


WITH  85  DIAGRAMS   AND   ILLUSTRATIONS 


SECOND  EDITION  CORRECTED. 


NEW    YORK 
D.  VAN    NOSTRAND   COMPANY 

23  MURRAY  AND  27  WARREN  STS. 
1904 


COPYRIGHT,  1903,  BY 
D.  VAN   NOSTRAND   COMPANY 


PREFACE 


THE  aim  of  this  book  is  to  present  a  comprehensive 
view  of  wireless  telegraphy,  its  history,  principles,  systems, 
and  possibilities  in  theory  and  practice.  In  considering 
inventions  controversy  has  been  avoided,  although  the 
claims  of  individual  inventors  have  been  carefully  defined. 
Because  of  the  complexity  of  the  subject  a  certain  amount 
of  allusion  in  one  part,  to  matters  dealt  with  in  another, 
has  been  inevitable ;  but  it  is  hoped  that  such  repetition 
may  prove  helpful  to  the  reader.  The  book  itself-  is  de- 
signed to  be  of  use  both  to  the  general  public  and  to  the 
technical  student. 

The  author  begs  to  acknowledge  to  the  publishers  his 
obligation  for  kind  co-operation  ;  to  the  Century  Magazine 
for  extracts  from  the  article  by  Mr.  McGrath  of  St.  Johns  ; 
and  to  the  Scientific  American  for  extracts  and  diagrams 
from  an  article  by  Mr.  A.  F.  Collins. 

CHARLES    H.  SEW  ALL. 

NEW  YORK,  September,  1903. 


196526 


TABLE  OF  CONTENTS. 


PART    I. 

PAGE 

PROPHECY i 

DISCOVERY 4 

ACHIEVEMENT .  u 

EXPLANATORY 24 

DESCRIPTIVE 38 

PART    II. 

INVENTORS  AND  INVENTIONS 91 

PART   III. 

THE  COMPARATIVE  MERITS  OF  WIRELESS  TELEGRAPHY  AND  OF 
TELEGRAPHY  BY  WIRES  AND  CABLES,  AND  THE  COMMER- 
CIAL OUTLOOK  FOR  EACH 125 

APPARATUS.  PART    IV' 

NOMENCLATURE 143 

TRANSMITTERS 145 

WAVE-RESPONSIVE-DEVICES 152 

WAVE-GATES 168 

SHIELDS        179 

CONDENSERS,  INDUCTANCE  COILS  AND  KEYS 182 

APPENDIX      .     .     .    .     .     .     .     ...    .-,. 190 

INDEX    .  226 


UNIVERSITY 
ilL/FORjji 


WIRELESS   TELEGRAPHY. 


PART  I. 


PROPHECY. 

"  Canst  them  send  lightnings,  that  they  may  go,  and  say  unto  thee, 
*  Here  we  are  ? ' "  —  JOB,  38th  chapter,  35th  verse. 

IN  1632  Galileo  wrote  a  dialogue  of  which  a  Latin  trans- 
lation appeared  at  Ley  den  in  1700.  Mr.  Robert  Sabine,  in 
his  work  on  the  Electric  Telegraph?-  rendered  into  English 
a  paragraph  from  the  Latin  version,  wherein  Sagredus,  one 
of  the  colloquists,  is  made  to  say : 

"  You  remind  me  of  one  who  offered  to  sell  me  a  secret  art,  by  which 
through  the  attraction  of  a  certain  magnet  needle  it  would  be  possible  to 
converse  across  a  space  of  two  or  three  thousand  miles.  And  I  said  to  him 
that  I  would  willingly  become  the  purchaser  provided  only  that  I  might 
first  make  a  trial  of  the  art,  and  that  it  would  be  sufficient  for  the  purpose 
if  I  were  to  place  myself  in  one  corner  of  the  sofa  and  he  in  the  other.  He 
replied  that  in  so  short  a  distance  the  action  would  be  scarcely  discernible : 
so  I  dismissed  the  fellow,  and  said  that  it  was  not  convenient  for  me  just 
then  to  travel  into  Egypt  or  Muscovy  for  the  purpose  of  trying  the  experi- 
ment, but  that  if  he  chose  to  go  there  himself  I  would  remain  in  Venice 
and  attend  to  the  rest." 

In  the  sixties  of  the  nineteenth  century  Mr.  Sabine 
supposed  this  expression  to  be  a  prescient  description  of 
telegraphy  with  wires.  In  1877  it  could  be  better  associ- 

1  D.  Van  Nostrand,  New  York,  1869. 
I 


2  WIRELESS   TELEGRAPHY. 

ated  with  telephone  transmission  over  a  conductor.  To- 
day, however,  we  can  readily  see  that  Galileo  wrote  of 
"Wireless  Telephony,"  an  art  not  quite  arrived.  It  will 
be  observed  that  as  translated  the  words  are  "  to  converse," 
not  "to  signal"  ;  and  the  correctness  in  translation  is  cor- 
roborated by  the  fact  of  the  action  at  short  distance  being 
undiscernible.  Readers  of  this  generation  will  understand 
that  between  two  persons  sitting  upon  the  same  sofa,  tele- 
phonic action  is  not  palpable ;  whereas  nearness  of  sender 
and  receiver  is  no  bar  to  the  observation  of  signals. 

It  may  be  that  Galileo  had  read  the  "  Prolusiones 
Academicae"  of  Strada,  published  in  1617,  and  which  de- 
scribed communication  at  a  distance  by  means  of  two 
needles  that  had  been  touched  with  lodestone.  These 
needles  were  mounted  upon  pivots.  If  either  of  them  were 
moved  it  caused  its  mate  to  turn  and  to  point  in  the  same 
direction  as  itself.  Possibly  Galileo  had  an  independent 
vision  of  wireless  communication,  seeing  farther  than 
Strada,  and  dared  make  of  it  but  guarded  mention.  It  is 
only  necessary  to  read  Galileo's  biography  to  realize  how 
disastrous  in  1632  might  have  been  the  consequences  of  an 
announcement  in  scientific  discovery. 

A  work  entitled  "Voyage  du  Jeune  Anacharsis  "  by  the 
Abbe  Barthelemy,  published  in  1788,  mentions  alphabetic 
dials,  having  hands  or  pointers  which  were  electrically 
magnetized ;  these  hands  on  the  clock  faces  being  analo- 
gous to  Strada's  description  one  hundred  and  seventy 
years  before. 

James  Bowman  Lindsay  in  1854  made  calculations  to 
demonstrate  that  stations  in  England  and  Scotland  could, 
without  wires,  signal  across  the  Atlantic  to  stations  in 
America. 


PROPHECY.  3 

Sir  William  Crookes,  1892,  reading  a  paper  entitled 
"Some  Possibilities  of  Electricity,"  said :  "Rays  of  light 
will  not  pierce  a  wall,  nor,  as  we  know  only  too  well,  a 
London  fog ;  but  electrical  vibrations  of  a  yard  or  more  in 
wave-length  will  easily  pierce  such  media,  which,  to  them, 
will  be  transparent.  Here  is  revealed  the  bewildering 
possibility  of  telegraphy  without  wires,  posts,  cables,  or  any 
of  our  present  costly  appliances."  Again  he  said  that 
Hertzian  rays  could  be  received  "on  a  properly  constituted 
instrument,  and  by  concerted  signals  messages  in  the  Morse 
code  can  thus  pass  from  one  operator  to  another." 

Tesla  (1893)  much  in  the  manner  outlined  by  his 
patents,1  predicted  the  transmission  through  space  and  with- 
out conductors  of  electrical  oscillations. 

Professor  Lodge  testifies  that  during  the  year  1894  Dr. 
Alexander  Muirhead  clearly  foresaw  the  telegraphic  im- 
portance of  the  transmission  of  Hertzian  waves. 

Professor  Ayrton,  an  English  scientist,  predicted,  in 
1897,  that  the  time  would  come  when  the  man  with  the 
electromagnetic  voice  in  one  part  of  the  world  would  call 
to  and  be  heard  by  the  man  with  the  electromagnetic  ear 
at  any  other  part  of  the  world ;  and  just  as  housemates 
call  to  one  another  in  the  same  dwelling  would  be  the 
long-distance  conversation ;  excepting  that  in  the  latter 
communication  only  the  selected  ear  might  catch  the 
sound. 

1  See  page  38. 


WIRELESS  TELEGRAPHY. 


DISCOVERY. 

CONNECTED  with  electrical  science  are  four  great  philos- 
ophers, Davy,  Faraday,  Helmholtz,  and  Hertz,  whose 
discoveries  all  but  span  the  nineteenth  century ;  and  in- 
terwoven with  the  work  of  those  four  discoverers  are  the 
important  achievements  of  Joseph  Henry,  Lord  Kelvin, 
Feddersen,  Maxwell,  Lodge,  Edison  and  Tesla. 

Sir  Humphry  Davy  was  born  in  1778,  and  consequently 
commenced  his  scientific  career  with  the  century.  Perhaps 
his  greatest  gift  to  electrical  progress  was  his  pupil  Michael 
Faraday.  The  latter,  in  1812,  happening  to  be  admitted 
to  one  of  Davy's  lectures,  became  at  first  his  pupil,  then 
his  amanuensis  and  assistant,  and  finally  in  1827  succeeded 
Sir  Humphry  as  Professor  of  Chemistry  at  the  Royal 
Institution  of  London.  This  happy  combination  in  Eng- 
land whereby  a  great  teacher  was  enabled  to  bequeath  to  a 
disciple  equally  talented  the  results  of  his  researches  was 
subsequently  duplicated  in  Germany  when  Heinrich  Hertz 
became  assistant  to  Helmholtz.  It  was  fortunate  also 
that  the  early  labors  of  Helmholtz  were  so  timed  that  he 
could  avail  himself  of  the  work  already  done  by  Davy  and 
Faraday.  The  death  of  Helmholtz  at  an  advanced  age 
in  1894,  and  of  Hertz  in  the  same  year  as  his  gifted 
master,  terminated  the  work  of  that  remarkable  quartet  of 
scientists. 

Chronologically  the  thread  of  discovery  begins  with 
Huyghens,  a  Dutch  philosopher  (born  1629,  died  1693), 


DISCOVERY.  5 

who  was  apparently  the  originator  of  the  undulatory  theory 
which  assumes  that  light  is  propagated  by  the  vibrations  of 
an  imponderable  medium  called  ether ;  and  although  for 
many  years  after  Huyghens  the  favored  idea  remained  that 
enunciated  by  Sir  Isaac  Newton  —  that  light  consists  of 
material  particles  projected  from  luminous  bodies  —  New- 
ton's hypothesis  has  since  been  rejected,1  and  that  of 
wave-motion  is  universally  recognized. 

In  1807,  when  Sir  Humphry  Davy  decomposed  potash 
by  electric-battery  power  there  was  inaugurated  that  won- 
derfully rapid  development  in  electrical  matters  which 
characterized  the  nineteenth  century.  To  this  develop- 
ment Davy  gave  the  initial  impulse  His  was  a  genius  so 
versatile  that  Coleridge  said,  "If  Sir  Humphry  had  not 
been  the  first  chemist  of  his  age,  he  probably  would  have 
been  its  first  poet."  At  the  age  of  twenty-three  Sir  Hum- 
phry's scientific  knowledge  and  his  eloquence  were  at- 
tracting in  London  brilliant  audiences.  He  delivered  a 
series  of  lectures  on  "Agricultural  Chemistry,"  which 
made  an  epoch  in  that  science ;  he  discovered  the  exhila- 
rating effect  produced  by  the  breathing  of  nitrous  oxide 
gas ;  his  lecture  on  "  Some  Chemical  Agencies  of  Elec- 
tricity "  obtained  for  him  the  prize  of  the  French  In- 
stitute ;  and  the  invention  of  the  miner's  safety  lamp 
brought  a  baronetcy  and  world-wide  fame.  Six  years  sub- 
sequent to  his  electrical  decomposition  of  potash,  Davy 
used  the  galvanic  battery  of  the  Royal  Institution,  consist- 
ing of  two  thousand  pairs  of  zinc  and  copper  plates,  and 
produced  between  two  carbon  electrodes  a  sparking  dis- 


1  The  Newton  hypothesis,  sometimes  called  the  "  corpuscular  theory  of  light,"  was  suc- 
cessfully controverted  by  Dr.  Thomas  Young  in  1773,  who  re-established  "  the  undulatory 
theory." 


6  WIRELESS   TELEGRAPHY. 

charge  four  inches  long  in  the  air,  and  seven  inches  long 
in  a  vacuum.  This  constituted  the  first  voltaic  arc. 

Faraday  in  1831  discovered  the  existence  of  a  current  in 
a  hollow  coil  of  wire  whenever  a  permanent  magnet  or  an 
electromagnet  was  introduced  into,  or  withdrawn  from, 
its  interior.  He  discovered  also  the  principles  of  inductive 
influences  between  electric  currents,  and  found  that  dif- 
ferent insulating  media  had  varying  capacities  to  produce 
inductive  effects.  Maxwell  quotes  Faraday  as  saying,  "  It 
was  allowable  to  admit  that  the  propagation  of  electricity 
might  be  effected  by  means  of  the  ether,  because  it  was 
probable  that  if  this  ether  existed  it  could  fill  another 
office  besides  serving  as  a  medium  for  the  transmission  of 
light." 

In  1 842  Professor  Joseph  Henry  of  Princeton,  United 
States,  drew  attention  to  the  fact  that  the  phenomena 
accompanying  the  discharge  of  a  Leyden  jar  was  oscillatory 
in  character,  and  Helmholtz  in  1847  confirmed  this.  Lord 
Kelvin  in  1853  demonstrated  mathematically  the  oscilla- 
tory effect,  and  Feddersen  in  1859  proved  it  by  experiment. 

Hermann  Helmholtz  was  born  at  Potsdam,  Prussia,  in 
1821,  and  was  consequently  beginning  his  life-work  when 
Faraday  had  reached  middle  age.  Like  Davy,  Helmholtz 
was  a  genius  of  great  versatility.  He  was  first  a  surgeon 
in  the  army,  and  during  his  medical  practice  invented  the 
ophthalmascope,  still  an  indispensable  piece  of  apparatus  for 
the  oculist.  He  was  metaphysician,  mathematician,  physi- 
ologist, and  physicist.  The  most  famous  writing  of  Helm- 
holtz was  his  essay  on  "Conservation  of  Energy,"  which 
firmly  established  that  law  ;  for  by  reason  of  diversified 
knowledge  he  was  able  to  bring  to  its  demonstration  facts 
from  all  departments  of  science.  In  the  same  paper 


DISCOVERY.  7 

Helmholtz  proclaimed  the  oscillatory  nature  of  a  discharge 
from  the  Leyden  jar;  and  explained  that  the  oscillations 
would  grow  weaker  and  weaker  until  their  entire  energy 
was  damped  out  by  opposing  resistances.  By  analyzing 
complex  tones  Helmholtz  made  science  explain  music,  and 
his  investigations  in  the  laws  of  sound  did  much  toward 
the  establishment  of  modern  wave  theories.  His  paper  on 
the  vortex  motion  in  fluids  was  probably  the  basis  for 
Lord  Kelvin's  hypothesis  that  all  matter  is  made  up  of 
small  vortices  of  fluid,  each  rotating  about  a  hollow  space. 
It  also  helped  to  formulate  Maxwell's  proposition. 

During  the  period  from  1863  to  1 873  there  was  developed 
the  philosophical  demonstration  by  James  Clerk  Maxwell, 
that  the  propagating  medium  of  electromagnetic  waves  was 
identical  with  that  of  light ;  and  although  he  was  not  able 
to  prove  it  by  experiment,  Maxwell  was  the  first  who  fully 
understood  what  is  now  admitted  to  be  the  true  nature 
of  electrical  phenomena.  Thus  by  1873  it  had  been 
established  that  light  with  a  velocity  of  1 86,000  miles  per 
second  consisted  of  a  wave  motion  produced  in  a  medium 
called  " ether,"  which  Maxwell  defined  as  "a  material  sub- 
stance of  a  more  subtle  kind  than  visible  bodies,  and 
supposed  to  exist  in  those  parts  of  space  which  are 
apparently  empty." 

Recapitulating,  Huyghens  in  the  seventeenth  century  had 
proclaimed  the  existence  of  ether  and  the  undulatory  mo- 
tion of  light,  and  this  was  confirmed  by  Dr.  Thomas  Young 
in  the  eighteenth.  In  the  nineteenth  century,  Henry, 
Helmholtz,  Kelvin,  and  Feddersen  demonstrated  that  the 
discharge  of  a  Leyden  jar  was  oscillatory.  Maxwell  con- 
tended that  if  the  velocity  of  propagation  of  electromag- 
netic disturbance  was  the  same  as  that  of  light,  which  had, 


8  WIRELESS   TELEGRAPHY. 

he  thought,  been  proved,  then  the  media  through  which 
either  light  or  electricity  was  transmitted  occupied  the 
same  space  and  must  be  identical  ;  and  the  difference  be- 
tween their  resultant  manifestations  depended  only  upon 
the  lengths  of  their  respective  waves.  Thus  the  matter 
stood  at  the  death  of  Maxwell  in  1879. 

As  has  been  said,  Heinrich  Hertz  was  a  pupil  of  Helm- 
holtz.  From  1883  to  1885  Hertz  occupied  at  Kiel,  Ger- 
many, the  chair  of  theoretical  physics,  and  in  the  latter  year 
was  appointed  Professor  of  Physics  in  the  Technical  High 
School  at  Carlsruhe.  During  the  delivery  of  a  lecture  at 
this  institution,  and  while  experimenting  with  a  Leyden  jar 
and  two  flat  coils  of  wire,  Hertz  observed  that  the  discharge 
of  the  jar  through  one  of  the  coils  would  induce  appreciable 
current  in  the  other  coil  ( although  the  jar  was  a  very  small 
one ),  provided  that  there  was  a  spark  gap  in  the  inducing 
coil.  This  accidental  discovery  came  to  a  man  who  has 
since  proved  to  be  perhaps  the  most  brilliant  experiment- 
alist and  the  ablest  physicist  the  world  has  seen.  Hertz 
demonstrated  that  the  reasoning  of  Maxwell  was  correct ; 
the  experiments  proving  conclusively  that  the  medium  which 
is  vibrated  by  light  and  the  medium  which  is  vibrated  by 
electromagnetism  is  one  and  the  same  ;  that  each  travels 
with  the  same  velocity ;  that  waves  of  electromagnetic 
disturbance  ( now  called  "  Hertzian  "  waves )  are  reflected 
from  conducting  surfaces  and  refracted  by  dielectric  sub- 
stances ;  and  are  plainly  analogous  to  the  reflection  of  light 
from  polished  surfaces  and  its  refraction  through  glass 
prisms. 

"This  great  discovery  of  Hertz,"  says  Professor  Lodge, 
"  was  by  no  means  his  only  one.  In  addition  to  his  well- 
known  essays  on  electric  waves,  which  marked  an  epoch  in 


DISCOVERY.  9 

experimental  physics,  no  less  than  eighteen  papers,  all 
original,  and  all  important,  were,  by  him,  contributed  to 
German  periodicals." 

After  the  experiments  at  Carlsruhe,  Hertz  in  1889  was 
called  to  the  chair  of  physics  in  the  University  at  Bonn. 
His  health  failed,  however,  and  he  died  at  Bonn  in  1 894. 
He  was  the  first  understandingly  to  transmit  electric  waves 
through  ether;  and  is  the  most  important  figure  in  the 
history  of  Wireless  Telegraphy.  From  his  discovery  in 
1886,  that  etheric  vibrations  would  result  from  the  passing 
of  sparks  across  an  air-gap,  began  the  development  of 
electric  transmission  without  conductors. 


10 


WIRELESS   TELEGRAPHY. 


ACHIEVEMENT.  II 


ACHIEVEMENT. 

THE  record  of  operative  electric  telegraphs  begins  in 
1774  with  that  of  Lesarge  at  Geneva,  Switzerland,  and 
prior  to  1837  twelve  had  been  constructed. 

In  July,  1837,  Steinheil  operated  in  England  a  telegraph 
line  twelve  miles  long,  which,  besides  its  two  terminal 
points,  was  provided  with  three  intermediate,  or  way,  sta- 
tions. He  used  but  one  wire,  employing  the  earth  as  a 
return  circuit.  There  were  alarm-bells  for  "calling,"  and 
the  signals  could  be  read  either  by  sound,  or  by  ink-marks 
recorded  upon  paper. 

In  1838  Professor  Joseph  Henry,  of  Princeton,  making 
with  an  electrical  machine  and  Ley  den  jar  a  one-inch 
spark  in  the  top  room  of  his  residence,  set  up  induced  cur- 
rents in  the  cellar  of  the  same  building. 

During  that  year  Steinheil  endeavored,  although  without 
success,  to  utilize  the  two  rails  of  a  steam  tramway  as  a 
telegraph  circuit,  but  suggested  the  possibility  of  doing 
away  altogether  with  conducting  wires. 

Professor  Morse,  who  had  conceived  his  idea  of  the  tele- 
graph in  1832,  did  not  succeed  in  operating  it  until  1838. 
His  plan  was  the  most  practical  of  any  brought  forward, 
and  proved  the  most  successful  ;  but  he  was  by  no  means, 
as  is  popularly  supposed,  the  originator  of  the  electric  tel- 
egraph with  wires.  There  seems,  however,  to  be  no  doubt 
but  that  he  was  the  very  first  to  signal  without  wires  ;  for 
on  December  i6th,  1842,  he  sent  a  wireless  telegram 


12  WIRELESS   TELEGRAPHY. 

across  a  canal  eighty  feet  wide ;  and  in  November,  1 844, 
Mr.  L.  D.  Gale,  acting  under  instructions  from  Professor 
Morse,  made  wireless  signals  across  the  Susquehanna 
River  at  Havre  de  Grace,  a  distance  of  nearly  one  mile. 
In  the  latter  experiment  Mr.  Gale  used,  as  a  source  of 
energy,  six  pairs  of  plates  in  the  form  of  a  galvanic 
battery.  He  found  that  the  best  results  were  obtained 
when  on  each  side  of  the  river  two  plates  were  immersed 
near  its  bank,  and  were  connected  by  an  insulated  wire 
stretched  along  each  shore  for  a  distance  three  times  as 
great  as  that  which  measured  either  path  of  the  crossing 
signals. 

The  few  chroniclers  of  wireless  telegraphy  have  all 
spoken  with  respect  and  affection  of  Mr.  James  Bowman 
Lindsay.  Several  years  after  Mr.  Gale's  experiments  on 
the  Susquehanna  River,  Lindsay,  having  no  knowledge  of 
what  Morse  had  done  in  America,  reached  the  same  results 
in  Scotland.  It  is  said  that  by  gradually  increasing  his 
distances,  Lindsay  succeeded  at  last  in  signaling  across 
the  Tay  where  the  river  is  two  miles  wide.  In  1854 
Lindsay  took  out  an  English  patent,  of  which  the  follow- 
ing brief  is  from  the  Abridgements  by  the  British  Com- 
missioners of  Patents  : 


"  This  invention  consists  of  a  method  of  completing  the  circuit  of  elec- 
tric telegraphs  through  water  without  submarine  cables  or  submerged 
wires  extending  across  such  water,  water  being  the  connecting  and  con- 
ducting medium  for  the  electric  fluid. 

"The  two  wires  respectively  connected  with  the  battery  and  signal 
instrument  on  one  side  of  the  water  are  attached  to  metal  balls,  tubes,  or 
plates  placed  in  the  water  or  in  moist  ground  adjacent  to  the  water.  The 
same  arrangement  is  placed  on  the  other  side  of  the  water ;  and  the  for- 
ward as  well  as  the  return  current  passes  between  the  respective  plates. 

"  It  is  preferred  to  place  the  plates  on  one  side  of  the  water  at  a  greater 


ACHIEVEMENT.  13 

distance  apart  than  the  distance  across  the  water ;  but  in  case  this  is  not 
practicable,  the  battery  power  must  be  augmented,  and  the  size  of  the 
immersed  plates  increased.  It  is  also  necessary  to  place  the  plates  for  the 
forward  current  opposite  to  each  other  and  the  plates  for  the  return  cur- 
rent opposite  to  each  other." 


Though  a  man  of  learning,  Lindsay  had  little  worldly 
wisdom.  He  was  one  of  the  best  linguists,  and  for  many 
years  employed  himself  upon  a  dictionary  of  fifty  lan- 
guages in  one  book.  He  foresaw  and  accurately  predicted 
the  universal  employment  of  electric  light  and  electric 
power.  He  thought  that  by  his  own  plan  of  wireless 
telegraphy  it  would  be  possible  to  span  the  Atlantic 
Ocean.  Lindsay  was  born  in  1799,  and  died  in  1862,  re- 
siding chiefly  at  Dundee,  Scotland.  He  was  a  bachelor, 
and  his  life  was  one  of  consistent  and  continuous  self-sac- 
rifice to  science.  It  is  said  that  during  the  year  1835  he 
lived  in  one  room,  which  was  illumined,  however,  by  an 
electric  lamp  whose  installation  was  the  work  of  his  own 
hands.  In  1859  ne  read  a  paper  before  the  British  Asso- 
ciation on  the  subject 'of  "Telegraphing  without  Wires," 
and  among  his  hearers  were  Faraday  and  Sir  William 
Thompson,  now  Lord  Kelvin.  While  Lindsay  was  not  an 
original  discoverer  in  wireless  telegraphy,  he  was  a  notable 
pioneer ;  and  his  unselfish  devotion  to  learning  has  won 
for  him  deserved  distinction. 

The  invention  of  the  telephone  in  1876  and  1877  fur- 
nished a  detector  of  great  delicacy,  and  immediately  after 
its  discovery  novel  electrical  phenomena  were  noted.  The 
author  in  1877  was  an  observer  of  those  remarkable  induc- 
tive effects  upon  neighboring  circuits  during  the  progress 
of  experiments  made  with  Edison's  "  Singing  Telephone  " 
over  a  wire  extending  from  New  York  to  Saratoga  Springs. 


14  WIRELESS   TELEGRAPHY. 

During  that  trial  I  had  a  Bell  telephone  receiver  in  cir- 
cuit upon  a  telegraph  wire  in  my  residence  on  the  east 
side  of  the  Hudson  River  at  Albany.  The  wire  to  which 
the  Bell  telephone  was  connected  ran  parallel  in  Albany 
with  the  transmitting  line  for  possibly  three  hundred  feet ; 
but  at  no  point  were  the  respective  circuits  less  than  thirty 
feet  apart.  That  particular  Edison  apparatus  transmitted 
simply  tones,  no  words.  The  receiving  record  of  the  Sing- 
ing Telephone  was  a  series  of  peculiarly  harsh  and  scrap- 
ing sounds,  so  that  from  the  notes  of  a  good  soprano  singer 
at  the  transmitter  there  were  audible  at  the  singing  re- 
ceiver nothing  but  the  different  pitches  of  those  tones,  all 
the  refinements  of  sound  being  lost.  Upon  the  unattached 
circuits  and  with  a  Bell  telephone  receiver,  however,  the 
harsh  features  were  eliminated  ;  and  while  no  articulate 
word  could  be  distinguished,  the  musical  flow  was  accurate, 
smooth,  and  pleasing.  Inductive  effects  from  the  same 
Singing  Telephone  were  also  manifest  at  Providence,  R.I., 
probably  by  reason  of  the  proximity  in  New  York  City  of 
the  wires  leading  to  Providence,  and  those  connected  with 
Saratoga. 

In  1882  Mr.  William  H.  Preece,  Engineer-in-Chief  of 
Government  Telegraphs  in  England,  succeeded  in  signaling 
across  the  Solent  from  England  to  the  Isle  of  Wight.  At 
two  different  points  plates  immersed  in  the  sea  near  one 
shore  were  put  in  line  with  similar  plates  near  the  opposite 
shore  ;  and  upon  each  side  two  of  the  plates  were  electri- 
cally connected  by  an  over-land  conductor.  The  arrange- 
ments of  the  circuits  was  the  same  as  that  used  by  Morse 
in  1842,  and  by  Lindsay  in  1854;  but  for  apparatus  Mr. 
Preece  had  an  advantage  over  his  predecessors  in  that  he 
could  use  a  receiving  telephone  to  detect  signals  ;  and  he 


ACHIEVEMENT.  15 

also  improved  upon  former  practice  by  employing  as  a 
transmitter,  and  in  place  of  a  contact  key,  a  rapidly  vibrat- 
ing reed  called  a  "buzzer,"  signals  appearing  at  the  receiv- 
ing end  as  long  and  short  buzzing  sounds.  At  other  times 
and  localities  in  England  Mr.  Preece  made  transmissions 
in  a  similar  way. 

The  year  1882  was  also  that  during  which  Professor 
Dolbear  in  America  filed  his  application  for  United  States 
Letters  Patent l  to  protect  devices  for  wireless  signaling. 
His  patent  is  further  discussed  under  "  Inventors  and  In- 
ventions." The  distances  over  which  he  succeeded  in 
sending  impulses  are  variously  reported  to  have  been  from 
half  a  mile  to  thirteen  miles. 

Mr.  Edison  (1885),  using  just  such  inductive  effects  as 
were  observed  in  1877,  when  his  Singing  Telephone  was 
tried,  signaled  through  space  to  a  moving  train  from  a 
wire  beside  the  railway. 

The  crowning  achievement  was  that  of  Hertz  in  1886. 
Across  the  little  gap  in  a  ring  of  wire  suspended  in  a  room 
(there  being  no  electrical  contact  with  the  charging  appara- 
tus) Hertz  made  tiny  sparks  appear,  as  the  result  of  the 
passage  across  another  and  longer  spark  gap  of  the  oscilla- 
tory discharge  from  a  Leyden  jar. 

Calzecchi  Onesti  about  1886  observed  the  coherency 
among  metal  filings  produced  by  the  impulsive  discharge 
of  a  previously  electrified  wire  or  coil. 

Second  in  importance  only  to  Hertz  is  the  connection 
with  Wireless  Telegraphy  of  Dr.  Oliver  Joseph  Lodge. 
This  eminent  scientist,  born  in  England  in  1851,  became 
Professor  of  Physics  at  the  new  University  of  Liverpool  in 
1880,  and  during  1887  was  elected  a  Fellow  of  the  Royal 

1  Printed  in  full  in  the  Appendix.     See  also  Edison  Patent  of  1885,  p.  96. 


16 


WIRELESS   TELEGRAPHY. 


Society.  At  the  date  of  Hertz's  first  etheric  transmis- 
sion, his  English  contemporary  was  conducting  experiments 
along  the  same  lines,  and  Hertz  said  that  in  time  Lodge 
would  undoubtedly  have  reached  the  same  results  as  him- 
self. Between  the  fil- 
ings tube  of  Onesti, 
1886,  and  that  of  Bran- 
ly,  1891,  there  inter- 
venes an  experiment  of 
Dr.  Lodge  in  1889, 
described  by  him  to  the 
Institution  of  Electri- 
cal Engineers  of  Lon- 
don in  1890.  He  had 
observed  "that  two 
knobs  sufficiently  close 
together,  far  too  close 
to  stand  any  voltage 
such  as  an  electroscope 
can  show,  would,  when 
a  spark  passes  between 
them,  actually  cohere, 
conducting,  if  a  single 
voltaic  cell  was  in  circuit,  an  ordinary  bell-ringing  cur- 
rent." With  permission  there  is  here  presented  from 
Dr.  Lodge's  "  Signalling  through  Space  without  Wires," 
the  diagram  shown  as  Fig.  3,  and  the  following  descrip- 
tion : 


Fig.  3. 


"  The  experiment  of  the  syntonic  Leyden  jars  can  be  conveniently 
shown  with  the  double  knob  or  1889  coherer.  The  pair  of  knobs  are 
arranged  to  connect  the  coatings  of  the  receiving  jar  (a  T.arge  condenser 
being  interposed  to  prevent  their  completing  a  purely  metallic  circuit), 


ACHIEVEMENT.  17 

and  in  circuit  with  them  is  a  battery  and  bell.  Every  time  the  receiving 
jar  responds  syntonically  to  the  electric  vibration  of  the  other  jar,  the 
knobs  cohere  (if  properly  adjusted)  and  the  bell  rings.  If  the  bell  is 
free  in  air  it  continues  ringing  until  the  knobs  are  gently  tapped  asunder ; 
but  if  the  bell  stands  on  the  same  table  as  the  knobs,  especially  if  it  rests 
one  foot  on  the  actual  stand,  then  its  first  stroke  taps  them  back  instantly 
and  automatically,  and  so  every  discharge  of  the  sending  jar  is  signaled 
by  a  single  stroke  of  the  bell.  Here  we  have  in  essence  a  system  of 
very  distinctly  syntonic  telegraphy,  for  the  jars  and  their  circuits  must  be 
accurately  tuned  together  if  there  is  to  be  any  response.  A  very  little 
error  in  tuning,  easily  made  by  altering  the  position  of  the  slider  (  see  s, 
Fig.  3),  will  make  them  quite  unresponsive  unless  the  distance  between 
them  is  reduced." 

Much  of  the  history  of  wireless  telegraphy  after  1889 
is  set  forth  in  detail  in  succeeding  divisions  of  this  work. 
Briefly,  Branly  (1890-1891)  made  the  filings  coherer 
that  is  sensitive  to  Hertzian  waves.  Dr.  Lodge  in  1893, 
having  learned  of  Branly's  results,  commenced  a  series  of 
experiments,  one  of  which  led  to  inclosing  the  filings  in  a 
vacuum,  and  another  to  the  making  of  a  more  positive  de- 
coherer  than  was  obtained  by  merely  mounting  the  electric 
bell  upon  the-  base  of  the  filings  tube.  In  1894  Lodge 
delivered  his  famous  lecture  reviewing  the  work  already 
done  with  Hertz's  oscillators,  with  Branly's  coherer,  and 
by  himself.  In  1895  was  accomplished  the  undertaking 
of  Count  Popoff  of  Russia,  described  under  "  Inventors  and 
Inventions."  In  the  same  year  Captain  Jackson,  by  direc- 
tion of  the  British  Board  of  Admiralty,  passed  electrical  sig- 
nals between  ships.  In  1896  Marconi  came  to  England, 
and  signaled  across  a  space  of  one  hundred  yards  at  the 
British  Post  Office  in  London.  Soon  afterwards  he  made 
a  successful  trial  of  two  miles  overland  on  Salisbury  Plain. 
In  May,  1897,  a  distance  of  nine  miles  over  water  was 
attained  by  Marconi,  and  from  that  time  his  signaling  dis- 


18  WIRELESS  TELEGRAPHY. 

tances   were   gradually    increased    until    he    spanned    the 
ocean.1 

Guglielmo  Marconi  was  born  at  Bologna,  Italy,  on  April 
25th,  1874.  His  father  is  an  Italian  nobleman,  and  his 
mother  of  Irish  nationality.  He  studied  at  Leghorn  under 
Professor  Rosa,  and  afterward  under  Righi  at  the  Univer- 
sity of  Bologna,  of  which  institution  he  is  a  graduate,  and 
has  been  interested  in  wireless  telegraphy  since  his  six- 
teenth year.  He  is  of  middle  height,  slim  in  figure,  with 
blue  eyes  and  brown  hair,  and  his  bearing  indicates  rather 
a  nervous  temperament.  Upon  November  25th,  1901,  Mr. 
Marconi  sailed  from  England,  his  destination  being  an  ex- 
perimental station  which  had  been  established  at  Cape 
Race,  some  eighty  miles  from  St.  Johns,  Newfoundland. 
When  interviewed  as  to  this  journey  by  reporters,  he  said 
to  them  that  there  was  a  possibility  of  signaling  over  three 
hundred  miles  of  sea,  and  felt  quite  sure  that  two  hundred 
miles  would  be  reached.  During  that  same  November, 
however,  the  author  was  privately  assured  by  an  official  of 
the  Marconi  Company  in  New  York  City,  that  within 
thirty  days  there  would  be  a  record  of  transatlantic  sig- 
naling. This  prediction  was  confirmed  by  the  event. 

There  had  been  constructed  at  Poldhu,  England,  and  at 
Cape  Cod,  Massachusetts,  stations  with  powerful  machinery 

1  "  Its  progress  has  not  been  slow.  Five  years  ago  my  system  worked  satisfactorily  over 
a  distance  of  about  two  miles.  Since  then  its  range  has  been  rapidly  increased,  until,  a  few 
months  ago,  by  means  of  improved  and  attuned  apparatus,  a  distance  of  over  two  hundred 
miles  was  successfully  bridged,  and  wireless  communication  at  this  distance  is  now  an 
everyday  occurence.  A  certain  commercial  application  of  my  system  has  already  been 
achieved.  In  all,  seventy  ships  carry  permanent  installations,  and  there  are  over  twenty 
land  stations  in  Great  Britain  and  on  the  continent  of  Europe,  besides  several  in  this  coun- 
try. To  what  further  extent  the  system  may  be  commercially  applied  is  not  easy  to  foretell. 
My  recent  successful  experiments  between  Poldhu  and  St.  Johns,  however,  give  great 
hopes  of  a  regular  transatlantic  wireless  telegraph  service  in  the  not  too  distant  future." 
From  Mar  corn's  prefatory  note  in  Century  of  March,  1902. 


ACHIEVEMENT.  19 

for  generating  electricity ;  and  especial  attention  had  been 
paid  to  the  vertical  conductors  or  wave-gates  by  which 
the  ether  waves  were  emitted  and  received.  These  struc- 
tures consisted  at  either  station  of  twenty  poles,  each  two 
hundred  and  ten  feet  high,  by  which  a  large  number  of 
wires  were  supported.  The  poles  and  wires,  both  in  Amer- 
ica and  England,  had  been  damaged  by  storm,  in  the  latter 
country  the  structure  at  Poldhu  being  practically  destroyed. 
Neither  had  been  fully  replaced.  The  aerial  distance 
between  Poldhu  and  Cape  Cod  was  some  six  hundred 
miles  farther  than  that  between  Poldhu  and  Cape  Race. 
Before  leaving  England,  Marconi  had  arranged  with  his 
Engineer  at  Poldhu  to  send  signals  in  a  certain  manner 
after  a  date  which  would  be  fixed  by  cablegram,  and  upon 
December  Qth  Poldhu  station  was  instructed  (by  cable)  to 
begin  sending  signals  every  day  at  three  o'clock  in  the 
afternoon,  and  to  continue  until  six  o'clock  evening,  these 
hours  by  Newfoundland  time  being  respectively  11.30 
A.M.  and  2.30  P.M.  The  signals  agreed  upon  were  rep- 
etitions of  the  letter  S  (by  telegraphic  code  three  short 

marks ),  to  be  repeated  a  certain  number  of  times  and 

then  discontinued,  for  intervals  of  three  minutes'  duration^ 
On  Thursday,  December  i2th,  1901,  at  12.30  P.M. 
Marconi  and  an  assistant,  Mr.  Kemp,  received  the  first 
transatlantic  signals.  During  the  appointed  hours  these 
signals  were  detected  a  number  of  times,  and  upon  the 
following  day,  Friday,  were  again  noticed.  The  public 
announcement  of  this  event  caused  great  excitement. 
Marconi  was  the  recipient  of  congratulatory  messages  from 
all  over  the  world,  and  during  the  next  few  weeks  he  was 
met  everywhere  with  a  series  of  ovations,  the  most  nota- 
ble, perhaps,  being  the  dinner  held  in  his  honor  at  the 


20  WIRELESS    TELEGRAPHY. 

Waldorf-Astoria  Hotel  in  New  York  City  by  the  American 
Institute  of  Electrical  Engineers. 

On  the  first  day  of  March,  1902,  Marconi  arrived  in 
New  York  City  from  England ;  and  declared  that  he  had 
received  on  a  moving  vessel  at  a  position  fifteen  hundred 
and  fifty-one  miles  from  the  sending  point 1  an  actual  mes- 
sage in  words ;  also  that  he  had  witnesses  to  prove  beyond 
peradventure  that  he  had  done  this  through  space  without 
wires  or  cables.  Further,  that  at  a  distance  two  thousand 
and  ninety-nine  miles l  from  the  sending  point  he  had 
received  signals  more  or  less  distinct  but  unmistakable. 

The  vessel  conveying  Marconi  and  his  telegraphic  devices 
was  the  steamship  Philadelphia.  Upon  the  following 
day,  March  2d,  arrived  at  New  York  the  Umbria  of  the 
Cunard  line ;  and  although  the  latter  ship  all  the  way 
across  the  Atlantic  had  been  in  the  same  receiving  zone  as 
the  Philadelphia,  and  was  actually  nearer  the  Cornish 
coast  during  the  time  the  latter  was  receiving  messages 
from  England,  not  a  word  or  signal  of  those  messages  was 
impressed  upon  the  apparatus  of  the  Cunard  steamer ; 
although  with  the  Campania  and  Etruria,  whose  instruments 
were  attuned  with  those  upon  the  Umbria,  perfect  com- 
munication was  had.  The  inventor  contended  that  two 
sets  of  instruments  of  different  electrical  tone  might  work, 
without  interference,  within  five  inches  of  each  other ;  that 
he  had  two  hundred  and  fifty  tunes  which  would  prevent 
" tapping  the  circuit";  that  the  secrecy  of  the  message 
was  complete.2 

1  See  frontispiece. 

2  "  It  seems  to  be  a  matter  of  popular  belief  that  any  receiver  within  effective  range  of 
the  transmitter  is  capable  of  picking  up  the  messages  sent,  or,  in  other  words,  that  there  can 
be  no  secrecy  of  communication  by  my  system.     Were  this  so,  a  very  important  limitation 
would  be  imposed  upon  the  practical  usefulness  of  the  system  ;  but  by  the  introduction  of 
important  and  radical  modifications  in  the  original  system,  and  by  a  systematic  application 


ACHIEVEMENT.  21 

In  the  communication  between  Cornwall  and  the  steam- 
ship all  the  messages  were  one  way,  all  from  the  station  to 
the  vessel.  Mr.  Marconi  explained  that  while  the  PJiila- 
dclphia's  equipment  admitted  the  reception  of  signals,  it 
had  not  a  sufficiently  powerful  transmitting  apparatus  to 
reach  to  England  ;  but  that  the  Cornwall  station  could  put 
forth  enough  energy  to  overcome  that  distance. 

So  far  as  is  generally  known,  there  was  from  the  time  of 
the  messages  to  5.  5.  Philadelphia  in  March,  1902,  no 
further  signaling  across  the  Atlantic  until  October  3ist  of 
the  same  year,  when  transoceanic  messages  were  received 
upon  the  Italian  warship  Carlo  Alberto  while  that  vessel  lay 
at  anchor  in  the  harbor  of  Sydney,  Nova  Scotia.  The  wire- 
less telegrams  were  transmitted  from  Poldhu.  The  distance 
covered  is  estimated  at  twenty-three  hundred  miles.  The 
Carlo  Alberto  had  been  placed  by  the  King  of  Italy  at  Mar- 
coni's disposal  as  an  assistance  to  wireless  experiments. 

It  was  on  Sunday,  December  2ist,  1902,  one  year  and 
nine  days  after  the  letter  S  from  Poldhu  was  heard  at 
Cape  Race,  that  Marconi  announced  the  transmission  of 
three  entire  messages  from  Table  Head  station  at  Glace 
Bay,  Cape  Breton,  to  Poldhu  station  in  Cornwall,  England, 
viz.  :  one  from  the  Governor  General  of  Canada  to  King 
Edward  of  England  ;  another  from  the  Commander  of  the 
Carlo  Alberto  to  the  King  of  Italy  ;  a  third  to  the  Times, 
in  London,  from  its  special  correspondent.  The  latter  was 
in  the  nature  of  formal  evidence,  and  read  as  follows  :  — 

"  Being  present  at  its  transmission  in  Signer  Marconi's  Canadian  station, 
I  have  the  honor  to  send  the  Times  the  inventor's  first  wireless  transatlantic 
message  of  greeting  to  England  and  Italy." 

of  the  principles  of  electrical  resonance,  this  objection  has,  in  very  great  measure,  been 
overcome."  —  From  Marconi 's  prefatory  note  in  Century  of  March,  iCj02- 


22  WIRELESS   TELEGRAPHY. 

Upon  January  iQth,  1903,  the  Marconi  Station  at 
Wellfleet,  Cape  Cod,  Massachusetts,  transmitted  the  follow- 
ing : 

His  MAJESTY,  EDWARD  VII., 

LONDON,  ENGLAND. 

In  taking  advantage  of  the  wonderful  triumph  of  scientific  research  and 
ingenuity  which  has  been  achieved  in  perfecting  a  system  of  wireless  tele- 
graphy, I  extend  on  behalf  of  the  American  people  most  cordial  greetings 
and  good  wishes  to  you  and  to  all  the  people  of  the  British.  Empire. 

THEODORE  ROOSEVELT. 
WELLFLEET,  MASS.,  JAN.  19,  1903. 

The  reply  which  follows  was  returned  by  cable  : 

SANDRINGHAM,  JAN.  19,  1903. 
THE  PRESIDENT, 

WHITE   HOUSE,  WASHINGTON,  AMERICA. 

I  thank  you  most  sincerely  for  the  kind  message  which  I  have  just  re- 
ceived from  you,  through  Marconi's  transatlantic  wireless  telegraphy.  I 
sincerely  reciprocate  in  the  name  of  the  people  of  the  British  Empire  the 
cordial  greetings  and  friendly  sentiment  expressed  by  you  on  behalf  of  the 
American  Nation,  and  I  heartily  wish  you  and  your  country  every  possible 
prosperity.  EDWARD  R.  AND  I. 

Mr.  Marconi  explained  that  his  apparatus  not  being 
quite  ready  for  long-distance  operation,  the  message  from 
President  Roosevelt  was  directed  to  be  relayed  by  Table 
Head,  Nova  Scotia,  station.  It  was  found,  however,  that 
the  Poldhu  station  in  England  had  been  able  to  copy  the 
telegram  while  it  was  being  sent  to  Table  Head. 

Upon  January  2ist,  1903,  the  Italian  Government  asked 
for  an  appropriation  of  $150,000  to  erect,  under  the  direc- 
tion of  Marconi,  wireless  telegraph  stations  with  a  capacity 
of  six  thousand  miles,  for  service  between  Italy  and  South 
America. 


ACHIEVEMENT. 


Fig.  4.  —Outside  the  Cabot  Tower  on  Signal  Hill,  St.  Johns,  Newfoundland. 

i.   Mr.  Kemp.  2.   Mr.  Marconi.  3-   Mr.  Paget.          4.   The  keeper  of  the  station. 

From  a  photograph.     Copyright  by  James  Vey.     By  Courtesy  of  the  Century  Company. 


24  WIRELESS   TELEGRAPHY. 


EXPLANATORY. 

WHAT  were  the  devices  and  methods  employed  to  ac- 
complish the  transmissions  ?  How  were  they  used  ?  Why 
did  they  produce  the  results  desired  ? 

Coherer.  —  The  prime  factor  is  the  coherer,  which  in 
Fig.  5  to  show  clearly  the  position  of  the  grains  g,  that 
constitute  the  kernel  of  the  whole  matter,  is  drawn  some- 
what out  of  proportion.  Those  metallic  grains  are  inclosed 
in  a  glass  tube,  G  G  G  G,  between  two  silver  plugs,  P  and 
P' ;  to  which  plugs  are  connected  platinum  wires,  W  and 
W.  When  proper  action  is  taken  at  a  transmitting  station 


Fig.  5- 

the  grains  g  at  a  receiving  point  cohere.  If,  after  cohesion 
is  established,  the  glass  tube  be  gently  tapped,  the  grains 
will  separate,  i.e.,  will  decohere.  When  these  minute  par- 
ticles are  together  they  close  an  electric  circuit,  producing 
an  effect  which,  on  account  of  the  delicacy  of  the  instru- 
ment, is  rather  weak,  but  which  may  be  made  through  a 
relay  to  close  another  electric  circuit  sufficiently  powerful 
to  produce  either  an  audible  signal,  as  when  a  telephone  or 
sounder  is  used,  or  to  exhibit  a  visual  one,  as  when  ink 


EXPLANATORY.  25 

marks  are  made  upon  paper  tape.  It  is  also  possible,  by 
means  of  this  second  and  stronger  electric  circuit,  auto- 
matically to  set  in  motion,  immediately  after  the  mark  has 
been  made,  a  vibrating  hammer  such  as  is  used  in  electric 
door-bells,  and  which  the  English  call  a  "trembler."  By 
directing  the  vibrating  hammer  against  the  coherer,  or 
against  anything  to  which  the  coherer  is  secured,  the  grains 
g  may  be  separated,  and  the  electric  devices  will  then  be  in 
position  to  make  another  mark.1 

Signals.  —  In  telegraphy  marks,  or  "  signals,"  are  made 
of  two  decidedly  differing  lengths,  designated  "the  long 
and  the  short."  Combinations  of  long  and  short  marks 
are  used  for  letters.  Upon  the  paper  ribbon  of  the  wireless 
telegraph  recorder  the  name  of  the  genius  who  signaled 
from  Poldhu  to  Cape  Race  would  appear  thus  : 

~M~     ~~A~      ~~R~        ~C~~  ~~0~        ~N~     T 

Circuits.  —  Fig.  6  is  a  diagram  devoid  of  many  details 
which  will  be  supplied  hereafter  in  other  drawings.  Upon 
the  receiving  side  letters  H,  B',  and  R  represent  respect- 
ively a  coherer  and  the  battery  and  relay  of  the  weak 
electric  circuit  before  noted.  On  the  transmitting  side  B  is 
a  battery,  and  K  a  key  for  closing  the  primary  circuit  of  a 
sparking  appliance  of  which  P  is  the  primary  winding  and 
L  the  secondary  part  of  a  "  step-up  "  induction  coil.  S  G 
stands  for  the  spark-gap.  Upon  each  closure  of  the  key  K, 
there  is  produced  sufficient  strain  to  cause  sparks  to  fly 
between  terminating  electrodes  T  T  of  the  secondary  coil 

1  See  Fig.  3,  Part  I.,  p.  16,  and  Fig.  31,  Part  II.,  p.  98,  and  accompanying  descriptions. 


UNIVERSITY 


26 


WIRELESS   TELEGRAPHY. 


L.  A  A'  are  vertical  wires  which  in  the  first  transatlantic 
transmission  were  respectively  maintained  in  position  by 
masts  at  Cornwall  and  by  a  kite  in  Newfoundland.  They 
are  sometimes  called  "antennae."  It  will  be  seen  that  at 
"Transmitter"  one  of  the  electrodes  T  is  in  connection 
with  the  high  wire  A,  while  the  other  is  put  to  earth  at  E. 
When  key  K  is  brought  onto  the  anvil  V,  an  electric  cir- 
cuit is  made,  and  the  current  in  it  by  inductive  influence  is 


Transmitter 
[B 


Receiver 


Fig.  6. 

communicated  to  the  secondary  coil  and  raised  in  pressure. 
The  sparking  across  S  G  becomes  the  center  of  a  disturb- 
ance from  which  waves  spread  in  all  directions.  These 
are  picked  up  by  any  vertical  wire  as  A'  and  pass  through 
P'  to  earth  at  E'.  In  the  receiving  apparatus,  the  sparking 
( exceedingly  weak  by  reason  of  dissipation  of  the  energy 
on  the  long  journey),  being  " stepped  up"  from  P'  to  L' 
is  now  through  the  filings  at  H,  causing  them  to  cohere, 
the  relay  R  is  energized  through  coherer,  and  by  a  local 
circuit  (not  shown  in  Fig.  6)  a  mark  is  made. 


EXPLANATORY.  27 

In  a  general  way  the  action  just  described  is  what  took 
place  at  Newfoundland  when  the  Poldhu  station  sent  the 
letter  s,  three  short  marks.  It  was  also  the  method 
employed  to  send  from  Poldhu  to  the  5.  5.  Philadelphia  at 
sea.  In  the  trial  to  Newfoundland  the  receiving  station 
used  an  ordinary  hand  ( listening  )  telephone  in  place  of  the 
relay  R  shown  in  Fig.  6,  a  telephone  receiver  being  much 
more  sensitive  than  a  relay.  Upon  the  Philadelphia,  how- 
ever, ink-marks  were  recorded  upon  paper  tape. 

TUNING. 

It  will  be  remembered  that  immediately  after  the  Corn- 
wall-Newfoundland demonstration,  Marconi,  upon  being 
asked  if  it  were  not  probable  that  he  received  the  sig- 
nal s  from  some  ship  or  station  other  than  the  Cornwall 
plant,  replied,  "  It  is  impossible  ;  I  was  tuned  only  for 
Poldhu." 

Theory  of  Electrical  Resonance.  —  To  understand  the 
devices  used  for  electrical  tuning  it  will  be  necessary  to 
consider  first  the  theory  by  which  "  electrical  resonance"  is 
explained,  and  then  the  analogies  that  are  used  to  demon- 
strate that  theory. 

It  is  supposed  that  all  matter,  solid,  liquid,  or  gaseous, 
is  made  up  of  molecules ;  and  that  these  molecules  are 
combinations  of  atoms  of  different  chemical  elements,  atoms 
being  quantitatively  the  smallest  divisions  of  matter,  and 
an  element  an  individual  substance,  as  distinguished  from 
those  substances  which  are  a  combination  of  two  or  more 
elementary  kinds  of  matter.  The  density,  and  to  an  extent 
the  weight,  of  any  substance  depends  upon  the  nearness  of 
the  molecules  to  one  another.  In  air,  or  other  gases,  they 


28  WIRELESS   TELEGRAPHY. 

are  widely  separated.  In  metals  they  are  very  close  to  one 
another.  In  either  substance  there  is  between  them  space, 
and  that  space  is  said  to  be  permeated  by  "ether."  Scien- 
tists have  not  yet  added  a  fourth  dimension  to  length, 
breadth,  and  thickness  ;  but  the  three  divisions  of  matter 
are  now  supplemented  by  a  fourth,  and  they  speak  of  the 
solid,  the  liquid,  the  gas,  and  the  ether. 

Analogy  of  Jelly.  —  An  analogy  to  ether  and  matter  is 
furnished  by  the  contents  of  a  vessel  containing  a  mixture 
of  lead  bullets  and  jelly.  Imagine  the  jelly  to  be  so  tremu- 
lous as  to  be  capable  of  vibrating  from  a  disturbance  by 
which  the  bullets,  being  much  more  inert,  move  so  little  as 
to  be  practically  still.  Further  imagine  that  the  jelly  be 
made  to  oscillate,  being  first  pushed  forward  and  then 
pulled  backward,  very  rapidly.  It  will  readily  be  under- 
stood that  before  the  forward  motion  of  the  jelly  has  over- 
come the  inertia  of  the  bullets,  the  backward  one  will  have 
reversed  and  neutralized  that  motion. 

Analogy  of  a  Pool  of  Water.  —  If  a  person  standing  upon 
one  side  of  a  pool  of  water  strikes  into  the  water  with  a 
paddle  each  time  in  the  same  direction  and  at  regular 
intervals,  so  that  he  maintains  a  rhythmical  beat,  it  will  be 
found  that  after  each  stroke  and  up  to  a  certain  maximum 
the  waves  caused  by  the  paddle  will  augment  in  size  ;  but 
that  if  strokes  be  afterward  made  at  irregular  intervals  the 
waves  will  decrease  in  volume.  Discord  will  tend  to  undo 
the  work  that  has  been  done  by  rhythm. 

Analogy  of  Spring  and  Timber.  —  Suppose,  as  in  Fig.  7, 
a  stick  of  timber  L  is  suspended  from  a  rigid  support  E  by 


EXPLANATORY. 


29 


a  spiral  steel  spring  C,  and  that  the  timber  be  given  a  push 
upward,  or  a  push  downward,  then  it  will  vibrate  a  certain 
number  of  times  per  minute.  If  it  be  pushed  gently  it  will 
move  slowly  through  a  small  space, 
if  pushed  forcibly  it  will  move 
more  quickly  through  a  greater 
space  ;  but  the  oscillations  in  a 
unit  of  time  will  always  be  the 
same.  This  rate  of  vibration  is 
governed  by  the  resiliency  of  the 
spring  C  and  the  weight  of  the  load 
L.  If  the  resiliency  of  the  spring 
be  increased,  or  the  weight  of  the 
timber  be  decreased,  the  rate  of 
vibration  will  be  quickened.  If  C 
be  made  less  springy,  or  L  be 
made  heavier,  the  rate  will  be 
slower.  To  change  the  rate  by  altering  either  or  both  of 
the  conditions  has  been  called  by  clockmakers  "  regu- 
lating" ;  Scientists  of  to-day  call  it  "tuning." 

Advantages  of  Harmonious  Action.  —  The  pushing  if 
continued  should,  in  order  to  get  the  best  results,  be  in 
accord  with  the  rate  of  the  apparatus ;  that  is  to  say,  the 
strokes  must  be  exactly  as  many  per  minute,  or  exactly 
one-half  as  many,  or  twice  as  many,  or  some  even  division 
or  multiple  of  the  rate.  Irregular  strokes  will  tend  to  stop 
the  motion  just  as  in  the  case  of  the  paddle  and  waves. 
Now  set  the  timber  L  upon  the  surface  of  the  water  on 
one  side  of  a  pool  of  considerable  width,  and  so  that  the 
crest  of  a  small  wave  will  just  uplift  it.  By  moving  the 
timber  and  timing  its  oscillations  the  rate  may  be  ascer- 


Fig.  7. 


30  WIRELESS   TELEGRAPHY. 

tained.  If  the  water  upon  the  far  side  of  the  pool  be  struck 
with  the  paddle  time  after  time  at  the  timber's  rate,  waves 
will  spread  from  the  paddle  ;  and  although  only  a  few  faint 
ripples  may  reach  the  timber-and-spring-device  they  will 
be  attuned  to  it,  and,  if  the  strokes  be  regularly  continued, 
each  wave  will  tend  to  increase  the  length  of  the  oscillation 
of  the  spring. 

At  Poldhu  a  powerful  source  of  vibration  was  sending 
waves  into  the  ether,  and  the  little  ripples  were  caught  at 
Newfoundland  by  a  delicate  receiving  apparatus  which  had 
been  adjusted  to  vibrate  at  the  same  rate  as  the  Cornwall 
transmitter. 

Fig.  8  represents  a  guitar,  which  instrument  may  be 
used  to  demonstrate  the  fact  that  air  waves  when  set  in 


Fig.  8. 

motion  by  one  string  of  a  certain  note  will  cause  to  vibrate 
another  string  tuned  to  the  same  note.  In  trying  this 
experiment,  to  avoid  troublesome  stretching  of  strings,  it 
will  be  advisable  to  keep  about  a  half-tone  below  "concert 
pitch."  When  the  A  string  is  brought  to  such  tension  as 
to  be  in  its  proper  relative  tune  with  the  E  string,  it  will 
sound  in  unison  with  the  latter,  whenever  the  E  is  stopped 
by  the  finger  pressing  the  E  firmly  against  fret  5. 


EXPLANATORY.  31 

Mechanical  Tuning.  —  To  ascertain  if  the  two  notes  are 
in  unison,  cut  a  piece  of  medium  writing-paper  to  a  size 
about  five-eighths  of  an  inch  square,  fold  it  one  way  in  the 
middle  and  set  it  astride  of  the  open  A  string.  When  the 
two  strings  are  properly  tuned,  and  the  E  string  is  struck 
below  the  stopped  point  at  fret  5,  the  paper  on  A  will  vi- 
brate so  strongly  as  to  be  perceptible  both  to  the  eye  and 
also  by  a  buzzing  noise  to  the  ear.  If  now  the  E  string  be 
stopped  either  on  the  4th  or  the  6th  fret,  or  if  the  tension 
on  the  A  string  be  increased  or  decreased  in  the  slightest 
degree,  the  paper  will  remain  motionless,  no  matter  how 
violently  the  E  string  may  be  set  in  motion.  Such  an 
operation  is  sometimes  called  " mechanical  tuning,"  and 
more  accurate  results  may  be  obtained  than  by  the  usual 
method  of  listening. 

Referring  back  to  the  spring  and  timber  demonstration 
in  a  pool  of  water  ( Fig.  7  ),  the  weight  of  the  A  string  is 
analogous  to  that  of  the  timber,  the  tension  upon  it  to  the 
elasticity  of  the  spring.  The  stopped  E  sets  up  waves  of 
exactly  the  same  rate  as  those  to  which  A  is  attuned. 

In  the  pool  the  waves  are  of  water  moving  a  few  feet 
per  second.  In  the  guitar  demonstration  the  waves  are  of 
air  moving  at  the  rate  of  1400  or  1500  feet  per  second. 
In  the  transatlantic  transmission  of  Marconi  the  waves 
were  of  ether,  traveling  186,000  miles  per  second. 

Electrical  Resonance  in  Practice.  —  It  is  hoped  that  the 
foregoing  illustrations  will  make  clear  the  principles  of 
electrical  resonance.  The  practice  is  illustrated  in  Fig.  9. 

Transmitting  Side.  —  B  is  a  battery  or  other  source  of 
energy.  P  is  the  primary  winding  of  an  induction  coil, 


32  WIRELESS   TELEGRAPHY, 

and  K  the  key  of  transmission.  L  is  a  secondary  wind- 
ing complementary  to  the  primary  P.  T  T  are  electrodes 
of  S  G  the  spark-gap.  C  is  a  condenser.  P2  and  L2  are 
respectively  the  primary  and  secondary  of  another  induc- 
tion coil  in  the  transmitting  apparatus  which  may,  by  way 
of  distinction,  be  called  a  transformer,  its  function  being 
to  convert  the  waves  that  oscillate  in  the  spark-gap  to  a 
still  higher  intensity.  D  is  a  variable  inductive  resistance 


Transmitter 


placed  in  the  circuit  between  the  vertical  wire  or  wave-gate 
A  and  the  earth  at  E.  At  the  transmitter  the  condenser 
C  is  analogous  to  the  resiliency  of  the  stopped  E  string  of 
Fig.  8,  and  L  2  and  D  represent  the  inertia  of  the  spring, 
or  the  load.  By  moving  the  pointer  d  the  load  may  be 
changed,  and  by  giving  the  condenser  more  or  less  surface 
the  force  of  oscillation  may  be  intensified  or  diminished. 


EXPLANATORY.  33 

Receiving  Side.  —  Looking  now  at  the  receiver  in  Fig.  9 
A'  is  the  vertical  wire.  The  changeable  inductive  resis- 
tance D'  and  primary  coil  P  3  of  a  transformer  is  placed 
in  that  part  of  the  wave  circuit  which  reaches  from  A'  to 
the  earth  at  E'.  D'  with  ?3  constitute  the  load,  being 
analogous  to  the  timber  in  Fig.  7.  Inductive  transference 
of  the  waves  from  ?3,  to  L3  and  L4,  increase  the  intensity 
of  the  faint  ripples  which  come  through  space  from  the 
vertical  wire  A  of  transmitter.  C'  is  a  condenser  placed 
in  a  bight  of  the  long  wire  which  forms  the  secondary 
winding  of  L3,  L4.  This  condenser  (  C' )  represents  the 
steel  spring  C  of  Fig.  7.  In  tuning  the  receiver,  either 
the  load  D'  ?3,  or  the  spring  C'  may  be  changed  to  in- 
crease or  decrease  the  rate  of  the  receiver.  Infinitesimal 
waves  passing  through  the  gaps  in  metallic  powder  of  H 
will  cause  those  grains  to  cohere,  and  so  close  the  electric 
circuit  H  B'  R.  Relay  R  translates  the  signal  into  a  more 
powerful  local  circuit,  which  actuates  an  ink-marking  regis- 
ter, and,  at  the  same  time,  causes  a  "  tapper  "  l  ( not  shown 
in  Fig.  9)  to  strike  the  glass  tube  H  and  "  decohere  "  the 
powder.  The  apparatus  is  then  ready  for  another  signal. 


LOCALIZATION. 

The  following  extract  of  a  letter  from  Dr.  A.  Fleming, 
which  was  published  in  the  London  Times,  October  4, 
1900,  will  serve  to  define  and  illustrate  the  term  used  as 
a  heading  for  this  division  : 

Two  operators  at  St.  Catherine's,  Isle  of  Wight,  were  instructed  to  send 
simultaneously  two  different  wireless  messages  to  Poole,  Dorset,  and  with- 
out delay  or  mistake  the  twTo  wrere  correctly  recorded  and  printed  down  at 
1  Similar  to  the  device  shown  in  Fig.  31,  Part  II. 


34  WIRELESS   TELEGRAPHY. 

the  same  time  in  Morse  signals  on  the  tapes  of  the  two  corresponding 
receivers  at  Poole. 

In  this  first  demonstration  each  receiver  was  connected  to  its  own 
independent  aerial  wire,  hung  from  the  same  mast.  But  greater  wonders 
followed.  Mr.  Marconi  placed  the  receivers  at  Poole  one  on  the  top  of  the 
other,  and  connected  them  both  to  one  and  the  same  wire,  about  forty  feet 
in  length,  attached  to  the  mast.  I  then  asked  to  have  two  messages  sent 
at  the  same  moment  by  the  operator  at  St.  Catherine's,  one  in  English  and 
the  other  in  French.  Without  failure,  each  receiver  at  Poole  rolled  out  its 
paper  tape,  the  message  in  English  perfect  on  one,  and  that  in  French  on 
the  other.  When  it  is  realized  that  these  visible  dots  and  dashes  are  the 
result  of  trains  of  intermingled  electric  waves  rushing  with  the  speed  of 
light  across  the  intervening  thirty  miles,  caught  on  one  and  the  same  short 
aerial  wire  and  disentangled  and  sorted  out  automatically  by  the  two  ma- 
chines into  intelligible  messages  in  different  languages,  the  wonder  of  it  all 
cannot  but  strike  the  mind. 

Your  space  is  too  valuable  to  be  encroached  upon  by  further  details,  or 
else  I  might  mention  some  marvelous  results  exhibited  by  Mr.  Marconi 
during  the  same  demonstrations,  of  messages  received  from  a  transmitter 
thirty  miles  away,  and  recorded  by  an  instrument  in  a  closed  room  merely 
by  the  aid  of  a  zinc  cylinder,  four  feet  high,  placed  on  a  chair.1  More 
surprising  is  it  to  learn  that,  while  these  experiments  have  been  proceeding 
between  Poole  and  St.  Catherine's,  others  have  been  taking  place  for  the 
admiralty  between  Portsmouth  and  Portland,  these  lines  of  communication 
intersecting  each  other;  yet  so  perfect  is  the  independence  that  nothing 
done  on  one  circuit  now  affects  the  other,  unless  desired. 

Mr.  Marconi  has  insisted  that  his  transmitted  signals 
are  perfectly  localized.  He  has  even  challenged  Professor 
Lodge  and  Mr.  Preece  either  to  interrupt  or  to  intercept 
them,  offering  the  use  of  his  company's  stations  should 
those  eminent  scientists  desire  to  experiment.  If,  however, 
they  try,  and  fail  to  catch  the  signals,  it  does  not  follow 
that  human  ingenuity  will  never  succeed  in  doing  so.  Un- 
less, indeed,  Marconi  has  means  other  than  those  generally 
known  to  the  electrical  profession,  it  is  believed  that  "syn- 
tony,"  as  it  is  called,  is  a  combination  not  difficult  to  unlock. 

1  See  Fig.  37,  Part  II. 


EXPLANATORY.  35 

The  company's  experts  claim  first,  that  their  spark-gap 
will  not  be  known  to  unauthorized  persons ;  again,  that 
their  coherer  may  be  made  so  insensitive  that  it  will  an- 
swer only  to  a  considerable  force  at  the  sending  station, 
and  that  all  energies  less  than  theirs  will  not  affect  it ; 
again,  that  in  addition  to  a  knowledge  of  the  force 
required  it  will  be  necessary  for  the  intercepter  to  know 
the  self-induction  ( the  load )  and  the  condenser  effect 
(the  resiliency).  It  would  seem,  however,  that  it  is  not 
necessary  to  ascertain  each  of  these  facts,  but  merely 
to  find  the  rate  of  beat  to  which  the  coherer  will  respond, 
and  that  may  be  any  combination  of  load  and  spring 
which  will  produce  the  right  wave-motion.  If,  then,  a 
would-be  tapper-in  exposes  a  number  of  coherers  differ- 
ently sensitized,  and  with  each  coherer  connected  with  a 
maximum  or  a  minimum  condenser  effect,  he  will  need 
only  to  vary  the  load  upon  each  coherer,  which  may  be 
very  rapidly  done.  Having  found  the  "rate,"  he  may 
"interrupt  "  as  well  as  "  intercept." 


QUANTITATIVE    DATA. 

Power.  —  In  quantitative  terms  authorized  statements 
in  the  March  Century,  1902,  give  the  energy  used  in  the 
Cornwall-Newfoundland  transmission  as  being  supplied  by 
a  40  h.  p.  alternating  current  dynamo,  having  an  initial 
pressure  of  two  thousand  volts  which  was  "stepped  up" 
to  fifty  thousand  volts.  There  were  at  Poldhu  twenty1 
masts,  each  two  hundred  and  ten  feet  high,  the  conductors 
upon  each  mast  being  in  electrical  connection  with  all  the 
others.  The  metal  spheres  forming  high-tension  terminals 

1  See  Fig.  66,  Part  IV. 


36  WIRELESS    TELEGRAPHY. 

of  the  transformers  were  separated  by  a  distance  which 
varied  from  about  ^  inch  to  about  -f^  inch.  At  the 
Newfoundland  station  the  aerial  wire  was  elevated  by  a 
kite  to  an  altitude  of  about  four  hundred  feet ;  its  swaying 
varied  the  altitude,  which  variation  was  a  serious  obstacle 
to  the  uniform  reception  of  signals.  The  coherer  used 
was  a  small  glass  tube  one  and  one-half  inches  long  and 
one-tenth  inch  internal  diameter.  Within  the  tube  were 
tightly  fitted  two  silver  plugs  separated  ^  inch.  This  lit- 
tle space  was  partly  filled  with  a  mixture  of  nickel  and  sil- 
ver filings  to  which  a  trace  of  mercury  had  been  added.1 

Comparative  Speed  of  Signal  Propagation  by  Wireless 
Telegraph  and  by  Cables.  —  Marconi  has  said  to  his  Eng- 
lish stockholders  that  whereas  the  speed  of  the  submarine 
cable-  is  directly  affected  by  length  of  transmission,  the 
wireless  system  is  not  in  the  least  affected  by  distance. 
That  "it  is  just  as  easy  to  work  at  high  speed  across  the 
Atlantic  or  Pacific  as  to  work  across  the  English  Channel." 
He  is  confident  of  establishing  direct  communication  be- 
tween England  and  New  Zealand.2  He  says  that  the  curv- 
ature of  the  earth  does  not  affect  the  signals,  and  that 
ultimately  he  will  be  able  to  send  them  all  around  the 
world. 

Marconi's  Conclusions.  —  From  that  excellent  article  in 
the  Century  Magazine  of  March,  1902,  already  mentioned, 
there  is  a  summing  up  of  Marconi's  conclusions  at  that 
date. 

Wireless  telegraphy  is  most  effective  over  marine  areas. 
Over  low  lying  country  two-thirds  of  marine  distance  may 

*-  See  description  of  "  silver  coherer  "  in  Part  IV. 
2  See  chart,  Fig.  39. 


EXPLANATORY.  37 

be  reached,  but  over  ordinary  diversified  country  the  po- 
tency of  vibrations  is  reduced  to  one-half  what  it  is  at  sea. 
High  hills  do  not  constitute  an  obstacle,  but  the  ground 
itself  retards  the  signals.  The  vibrations  seem  to  reach 
slightly  farther  in  fog  than  in  fine  weather.  Atmospheric 
conditions  do  not  seriously  affect  the  signals.  Electrical 
disturbances  are  their  only  foe.  Indications  are  that  a 
pole  two  hundred  feet  high  gives  the  best  results.  With  a 
a  balloon  or  kite  elevated  to  four  hundred  feet,  the  wire 
must  necessarily  be  very  slight,  and  the  ceaseless  swaying 
of  the  upholder  also  interferes.  A  horizontal  wire  (as  an 
antenna)  gives  no  energy.  No  advantage  in  marine  signal- 
ing is  gained  by  setting  a  pole  on  a  high  hill.  Proximity 
to  the  sea  is  desirable  and  a  low-lying  spit  of  land  the  best. 
Some  geological  formations  are  perverse,  others  are  respon- 
sive. 


38  WIRELESS   TELEGRAPHY. 


DESCRIPTIVE. 

TESLA  1    IN    WIRELESS    TRANSMISSION. 

Tesla's  Proposed  Plan  of  1893.  —  Nikola  Tesla  devoted 
himself  early  to  the  problem  of  transmitting  electrical 
energy  without  wires,  not  only  for  telegraphic,  but  also  for 
industrial  purposes.  In  February  and  March,  1893,  he 
delivered  lectures  before  the  Franklin  Institute  in  Phila- 
delphia and  the  National  Electric  Light  Association  in  St. 
Louis,  in  which  he  advanced  a  plan  of  wireless  transmis- 
sion, and  expressed  his  conviction  that  "  it  certainly  is 
possible  to  produce  some  electrical  disturbance  sufficiently 
powerful  to  be  perceptible  by  suitable  instruments  at  any 
point  of  the  earth's  surface." 

In  describing  his  plan  in  detail  he  says  : 

"  Assume  that  a  source  of  alternating  currents,  j,  be  connected,  as  in  Fig. 
10,  with  one  of  its  terminals  to  earth  (convenient  to  the  water  mains),  and 


Fig.  10. 

with  the  other  to  a  body  of  large  surface,  P.     When  the  electric  oscillation 
is  set  up,   there  will  be  a  movement  of  electricity   in  and  out   of    P,  and 

1  TESLA,  NIKOLA,  born  at  Smiljan,  Lika,  Austria-Hungary,  in  1857.  A  noted  physicist 
and  electrician.  He  came  to  the  United  States  in  1884  with  a  view  of  developing  motors 
based  on  his  discovery  of  the  rotating  magnetic  field  ;  this  he  completed  in  1888.  He  has  in- 
vented a  number  of  methods  and  appliances  in  the  line  of  electrical  vibrations  aiming  at  the 
production  of  efficient  light  with  lamps  without  filaments,  and  the  production  and  transmis- 
sion of  power  and  intelligence  without  wires.  On  his  discovery  of  the  action  of  air  or  gase- 
ous matter  when  subjected  to  rapidly  alternating  electrostatic  stresses  is  based  the  modern 
art  of  insulating  currents  of  very  high  tension.  He  has  also  constructed  steam-engines  and 
electrical  generators  (oscillators)  with  which  otherwise  unattainable  results  are  obtained.  — 
Century  Dictionary  and  Cyclopedia,  1895. 


WIRELESS    TELEGRAPHY.  39 

alternating  currents  will  pass  through  the  earth,  converging  to  or  diverging 
from  the  point  C,  where  the  ground  connection  is  made.  In  this  manner 
neighboring  points  on  the  earth's  surface  within  a  certain  radius  will  be 
disturbed.  But  the  disturbance  will  diminish  with  the  distance,  and  the 
distance  at  which  the  effect  will  still  be  perceptible  will  depend  on  the 
quantity  of  electricity  set  in  motion.  Since  the  body  P  is  insulated,  in 
order  to  displace  a  considerable  quantity  the  potential  of  the  source  must 
be  excessive,  since  there  would  be  limitations  as  to  the  surface  of  P.  The 
conditions  might  be  adjusted  so  that  the  generator,  or  source,  s,  will  set  up 
the  same  electrical  movement  as  though  its  circuit  were  closed.  Thus  it 
is  certainly  practicable  by  means  of  proper  machinery  to  impress  an 
electric  vibration,  at  least  of  a  certain  low  period,  upon  the  earth.  Theo- 
retically it  should  not  require  a  great  amount  of  energy  to  produce  a  dis- 
turbance perceptible  at  great  distance,  or  even  all  over  the  surface  of 
the  globe.  Now,  it  is  quite  certain  that  at  any  point  within  a  certain 
radius  of  the  source,  s,  a  properly  adjusted  self-induction  and  capacity 
device  can  be  set  in  action  by  resonance.  Not  only  can  this  be  done, 
but  another  source,  s,1  Fig.  10,  similar  to  s  or  any  number  of  such  sources 
may  be  set  to  work  in  synchronism  with  the  latter,  and  the  vibration  thus 
intensified  and  spread  over  a  large  area ;  or  a  flow  of  electricity  produced 
to  or  from  the  source  s,1  if  the  same  be  of  opposite  phase  to  the  source,  s. 
Proper  apparatus  must  first  be  produced,  by  means  of  which  the  problem 
can  be  attacked,  and  I  have  devoted  much  thought  to  this  subject." 

In  the  same  lectures  he  showed  a  number  of  novel  ex- 
periments, among  which  was  the  operation  of  a  variety  of 
devices  by  using  one  wire,  instead  of  two  as  is  usual  in  elec- 
trical connections.  He  continued  investigations  along  these 
lines,  and  in  1898  had  already  developed  apparatus  of  great 
power,  giving  a  pressure  of  four  million  volts  and  dis- 
charges extending  through  sixteen  feet,  which  at  that  time 
were  considered  remarkable.1 

Tesla's  First  Two  Patents  on  Methods  and  Apparatus 
for  the  Wireless  Transmission  of  Energy. —  The  patents 
are  numbered  645,576  and  649,621,  and  were  issued 

1  See  Electrical  Review,  New  York,  October  26,  1898. 


40 


DESCRIPTIVE. 


Fig.  xi. 

Diagram  of  wireless  transmission  accompanying  Tesla's  U.  S.  patents  No.  645,576  and 
No.  649,621.  The  transmitter  comprises  a  generator  of  electric  oscillations  G,  a  primary 
conductor  C,  and  a  secondary  coil  A  B,  which  is  connected  to  ground  and  to  an  elevated 
terminal  D,  and  tuned  to  the  oscillations  of  the  generator.  The  receiving  apparatus  has  a 
similarly  arranged  coil  A'  D'  tuned  to  the  transmitted  oscillations,  and  associated  with  a 
secondary  circuit  containing  the  receiving  devices.  The  terminals  D  and  D'  are  maintained 
above  the  surrounding  objects,  the  height  being  determined  by  the  amount  and  quality  of 
the  work  to  be  performed.  The  length  of  the  grounded  conductors  A  D  and  A'  D'  is 
preferably  made  equal  to  one  quarter  of  the  wave  length  of  the  oscillations.  The  trans- 
mitter and  receiver  may  be  thousands  of  miles  apart. 


DESCRIPTIVE.  41 

respectively  March  2Oth,  and  May  I5th,  1900.  The  origi- 
nal application  covering  both  inventions  was  filed  September 
2nd,  1 897.  The  system,  as  described  by  the  inventor  in 
these  patents,  is  radically  different  from  the  Hertzian,  both 
in  the  methods  and  apparatus  employed.  In  the  Hertzian 
system,  the  energy  is  transmitted  to  the  receiver  by  elec- 
tro-magnetic waves  which  pass  out  laterally  from  the 
transmitting  wire  into  space.  In  Tesla's  system  the  energy 
radiated  is  not  used,  but  a  current  is  led  to  earth  and  to 
an  elevated  terminal,  and  the  energy  is  transmitted  by  a 
process  of  conduction.  Quoting  from  one  of  his  patents  : 

"  It  is  to  be  noted  that  the  phenomenon  here  involved  in  the  trans- 
mission of  electrical  energy  is  one  of  true  conduction,  and  is  not  to  be 
confounded  with  the  phenomena  of  electrical  radiation  which  have  here- 
tofore been  observed,  and  which,  from  the  very  nature  and  mode  of  propa- 
gation, would  render  practically  impossible  the  transmission  of  any  appreci- 
able amount  of  energy  to  such  distances  as  are  of  practical  importance." 

The  arrangement  of  his  transmitting  and  receiving 
circuits  is  illustrated  in  Fig.  n,  and  will  be  understood 
with  reference  to  the  explanatory  note. 

As  characteristic  of  these  inventions  the  following  two 
claims  may  be  quoted  : 

"  The  method  hereinbefore  described  of  transmitting  electrical  energy 
through  the  natural  media,  which  consists  in  producing  at  a  generating 
station  a  very  high  electrical  pressure,  causing  thereby  a  propagation  or 
flow  of  electrical  energy,  by  conduction,  through  the  earth  and  the  air 
strata,  and  collecting  or  receiving  at  a  distant  point  the  electrical  energy  so 
propagated  or  caused  to  flow. 

The  combination  with  a  transmitting  coil  or  conductor  connected  to 
ground  and  to  an  elevated  terminal  respectively,  and  means  tor  producing 
electrical  currents  or  oscillations  in  the  same,  of  a  receiving  coil  or  conduc- 
tor similarly  connected  to  ground  and  to  an  elevated  terminal,  the  said  coil 
or  coils  having  a  length  equal  to  one  quarter  of  the  wave  length  of  the 
disturbance  propagated,  as  set  forth." 


42  WIRELESS    TELEGRAPHY. 

Description  of  Transmitter  Giving  Four  Million  Volts.  - 
In  describing  a  special  apparatus  Tesla  says  : 

"  The  transmitting  apparatus  was  in  this  case  one  of  my  electrical 
oscillators,  which  are  transformers  of  a  special  type,  now  well  known  and 
characterized  by  the  passage  of  oscillatory  discharges  of  a  condenser 
through  the  primary.  The  source  G,  forming  one  of  the  elements  of  the 
transmitter,  was  a  condenser  of  a  capacity  of  about  four  one-hundr.edths  of 
a  microfarad,  and  was  charged  from  a  generator  of  alternating  currents  of 
fifty  thousand  volts  pressure,  and  discharged  by  means  of  a  mechanically 
operated  break  five  thousand  times  per  second  through  the  primary  C. 
The  latter  consisted  of  a  single  turn  of  stout,  stranded  cable  of  inappreciable 
resistance  and  of  an  inductance  of  about  eight  thousand  centimeters,  the 
diameter  of  the  loop  being  very  nearly  two  hundred  and  forty-four  centime- 
ters. The  total  inductance  of  the  primary  circuit  was  approximately  ten 
thousand  centimeters,  so  that  the  primary  circuit  vibrated  generally  accord- 
ing to  adjustment,  from  two  hundred  and  thirty  thousand  to  two  hundred 
and  fifty  thousand  times  per  second.  The  high-tension  coil  A  in  the  form 
of  a  flat  spiral  was  composed  of  fifty  turns  of  heavily  insulated  cable  No.  8 
wound  in  one  single  layer,  the  turns  beginning  close  to  the  primary  loop 
and  ending  near  its  center.  The  outer  end  of  the  secondary  or  high-tension 
coil  A  was  connected  to  the  ground. 

The  primary  and  secondary  circuits  in  the  transmitting  apparatus  being 
carefully  synchronized,  an  electromotive  force  from  two  to  four  million  volts 
and  more  was  obtainable  at  the  terminals  of  the  secondary  coil  A." 

Curious  Phenomena  Produced. —  Tesla's  apparatus  seems 
to  be  capable  of  peculiar  actions.  He  says : 

"  For  example,  a  conductor  or  terminal,  to  which  impulses  such  as  those 
here  considered  are  supplied,  but  which  is  otherwise  insulated  in  space  and 
is  remote  from  any  conducting-bodies,  is  surrounded  by  a  luminous  flame-like 
brush  or  discharge  often  covering  many  hundreds  or  even  as  much  as 
several  thousands  of  square  feet  of  surface,  this  striking  phenomenon  clearly 
attesting  the  high  degree  of  conductivity  which  the  atmosphere  attains 
under  the  influence  of  the  immense  electrical  stresses  to  which  it  is 
subjected.  This  influence  is,  however,  not  confined  to  that  portion  of  the 
atmosphere  which  is  discernible  by  the  eye  as  luminous,  and  which,  as  has 
been  the  case  in  some  instances  actually  observed,  may  fill  the  space  within 
a  spherical  or  cylindrical  envelope  of  a  diameter  of  sixty  feet  or  more,  but 
reaches  out  to  far  remote  regions,  the  insulating  qualities  of  the  air  being, 


NIKOLA   TESLA. 


DESCRIPTIVE.  43 

as  I  have  ascertained,  still  sensibly  impaired  at  a  distance  many  hundred 
times  that  through  which  the  luminous  discharge  projects  from  the  terminal 
and  in  all  probability  much  farther." 

The  conductivity  imparted  to  the  air  by  these  currents 
Tesla  proposes  to  utilize  in  the  wireless  transmission  of 
power  on  an  industrial  scale. 

Transmission  of  Enormous  Energy  Over  Vast  Dis- 
tances. —  "  From  my  experiments  and  observations  I  con- 
clude tJiat  with  electromotive  impulses  not  greatly  exceeding 
fifteen  or  tiventy  million  volts  the  energy  of  many  thousands 
of  Jiorse-poiver  may  be  transmitted  over  vast  distances, 
measured  by  many  hundreds  and  even  thousands  of  miles, 
vvitJi  terminals  not  more  than  thirty  to  thirty-five  tJiousand 
feet  above  the  level  of  the  sea  ;  and  even  this  comparatively 
small  elevation  will  be  required  chiefly  for  reasons  of  econ- 
omy, and  if  desired  it  may  be  considerably  reduced,  since, 
by  such  means  as  have  been  described,  practically  any 
potential  that  is  desired  may  be  obtained  and  the  currents 
through  the  air  strata  may  be  rendered  very  small,  whereby 
the  loss  in  the  transmission  may  be  reduced.  It  will  be 
understood  that  the  transmitting  as  well  as  the  receiving 
coils,  transformers,  or  other  apparatus  may  be  in  some 
cases  movable  —  as,  for  example,  when  they  are  carried  by 
vessels  floating  in  the  air,  or  by  ships  at  sea." 

To  express  this  idea  in  other  language,  if  one  captive 
balloon  were  put  at  seven  miles'  elevation  over  Niagara  Falls, 
and  another  balloon  at  the  same  height  in  France,  energy 
from  a  dynamo  at  the  former  station  might  without  undue 
loss  in  transmission  be  made  to  set  in  motion  upon  French 
territory  electric  motors,  or  to  supply  the  power  to  illumine 
electric  lamps. 


44  WIRELESS   TELEGRAPHY. 

Tesla's  "Telautomata."—  On  July  i,  1898,  Mr.  Tesla 
filed  an  application  for  another  American  Patent,  No. 
613,809.  Its  first  claim  is  an  excellent  brief.  It  reads : 

"  The  improvement  in  the  art  of  controlling  the  movements  and  opera- 
tion of  a  vessel  or  vehicle  herein  described,  which  consists  in  producing 
waves  or  disturbances  which  are  conveyed  to  the  vessel  by  the  natural 
media,  actuating  thereby  suitable  apparatus  on  the  vessel  and  effecting  the 
control  of  the  propelling  engine,  the  steering  and  other  mechanism  by  the 
operation  of  the  said  mechanism  as  set  forth." 

Methods  Described.  —  The  inventor  describes  a  number 
of  methods  for  producing  waves.  The  preferred  one 
seems  to  be  the  "  passing  through  the  conducting  path 
currents  of  a  specially  designed  high  frequency  alternator, 
or,  better  still,  those  of  a  strongly  charged  condenser,"  and 
then  "adjusting  the  circuit  on  the  moving  body  so  as  to  be 
in  exact  electromagnetic  synchronism  with  the  primary  dis- 
turbances ; "  and  he  says  that  in  such  a  way  "  this  in- 
fluence may  be  utilized  at  great  distances." 

Application  to  Warfare. —  In  summing  up  the  many  use- 
ful purposes  to  which  this  invention  may  be  applied,  the 
pantentee  thinks  its  "  greatest  value  will  result  from  its 
effect  upon  warfare  and  armaments,  for  by  reason  of  its 
certain  and  unlimited  destructiveness  it  will  tend  to  bring 
about  and  maintain  perfect  peace  among  nations."  It  may 
be  inferred  that  this  refers  more  especially  to  the  moving 
and  direction  of  torpedoes. 

In  the  Tesla  system  methods  of  electrical  conversion  by 
means  of  condenser  discharges  and  the  so-called  "Tesla 
coil  "  play  an  important  part.  The  earliest  records  of  these 
inventions  in  the  U.  S.  Patent  Office  date  from  1891. 


DESCRIPTIVE.  .  45 

v, 

Method  of  Electrical  Conversion  by  Condenser  Dis- 
charges. —  This  method  is  described  in  Patent  Number 
462,418  of  November  3,  1891  (application  filed  February 
4,  1891). 

Quoting  in  the  language  of  the  inventor : 

"  I  employ  a  generator,  preferably  of  very  high  tension,  and  capable  of 
yielding  either  direct  or  alternating  currents.  This  generator  I  connect  up 
with  a  condenser  or  conductor  of  some  capacity,  and  discharge  the  accumu- 
lated electrical  energy  disruptively  through  an  air-space  or  otherwise  into 
a  working  circuit  containing  translating  devices  and,  when  required,  conden- 
sers. These  discharges  may  be  of  the  same  direction  or  alternating  and 
intermittent,  succeeding  each  other  more  or  less  rapidly  or  oscillating  to 
and  fro  with  extreme  rapidity.  In  the  working  circuit,  by  reason  of  the 
condenser  action,  the  current  impulses  or  discharges  of  high  tension  and 
small  volume  are  converted  into  currents  of  lower  tension  and  greater  vol- 
ume. The  production  and  application  of  a  current  of  such  rapid  oscillations 
or  alternations  (the  number  may  be  many  millions  per  second)  secures, 


( 

T 

•      i        « 

B                                                                            c 

)       ( 

^   Qc 

fj 

T 

Fig.  12. 

among  others,  the  following  exceptional  advantages:  First,  the  capacity 
of  the  condensers  for  a  given  output  is  much  diminished ;  second,  the 
efficiency  of  the  condensers  is  increased  and  the  tendency  to  become  heated 
reduced  ;  and,  third,  the  range  of  conversion  is  enlarged.  I  have  thus  suc- 
ceeded in  producing  a  system  or  method  of  conversion  radically  different 
from  what  has  been  done  heretofore  —  first,  with  respect  to  the  number  of 
impulses,  alternations,  or  oscillations  of  current  per  unit  of  time,  and,  second, 
with  respect  to  the  manner  in  which  the  impulses  are  obtained.  To  express 
this  result,  I  define  the  working  current  as  one  of  an  excessively  small 
period  or  of  an  excessively  large  number  of  impulses  or  alternations  or  oscil- 
lations per  unit  of  time,  by  which  I  mean  not  a  thousand  or  even  twenty  or 
thirty  thousand  per  second,  but  many  times  that  number,  and  one  which  is 
made  intermittent,  alternating,  or  oscillating  of  itself  without  the  employ- 
ment of  mechanical  devices." 


46  WIRELESS    TELEGRAPHY. 

Referring  to  the  diagram  in  Fig.  1 2  : 

"  A  represents  a  generator  of  high  tension ;  B  B,  the  conductors  which 
lead  out  from  the  same.  To  these  conductors  are  connected  the  conduc- 
tors C  of  a  working  circuit  containing  translating  devices,  such  as  incandes- 
cent lamps  or  motors  G.  In  one  or  both  conductors  B  is  a  break  D,  the 
two  ends  being  separated  by  an  air-space  or  a  film  of  insulation,  through 
which  a  disruptive  discharge  takes  place.  F  is  a  condenser,  the  plates  of 
which  are  connected  to  the  generating-circuit. 

The  discharges  will  follow  each  other  the  more  rapidly  the  more  nearly 
the  rate  of  supply  from  the  generator  equals  the  rate  at  which  the  circuit 
including  the  generator  is  capable  of  taking  up  and  getting  rid  of  the 
energy.  Since  the  resistance  and  self-induction  of  the  working  circuit  C 
and  the  rapidity  of  the  successive  discharges  may  be  varied  at  will,  the  cur- 
rent strengths  in  the  working  and  in  the  generating  circuit  may  bear  to  one 
another  any  desired  relation. 

Tesla  Coil.  —  This  invention  is  first  described  in  Patent 
No.  454,622  of  June  23,  1891  (application  filed  April  5th, 
1891).  In  the  description  the  inventor  says  : 

"  To  produce  a  current  of  very  high  frequency  and  very  high  potential, 
certain  well-knowrn  devices  may  be  employed.  For  instance,  as  the  primary 
source  of  current  or  electrical  energy,  a  continuous-current  generator  may 
be  used,  the  circuit  of  which  may  be  interrupted  with  extreme  rapidity  by 
mechanical  devices,  or  a  magneto-electric  machine  specially  constructed  to 
yield  alternating  currents  of  very  small  period  may  be  used,  and  in  either 
case,  should  the  potential  be  too  low,  an  induction-coil  may  be  employed  to 
raise  it ;  or,  finally,  in  order  to  overcome  the  mechanical  difficulties,  which 
in  such  cases  become  practically  insuperable  before  the  best  results  are 
reached,  the  principle  of  the  disruptive  discharge  may  be  utilized.  By 
means  of  this  latter  plan  I  produce  a  much  greater  rate  of  change  in  the 
current  than  by  the  other  means  suggested,  and  in  illustration  of  my 
invention  I  shall  confine  the  description  of  the  means  or  apparatus  for  pro- 
ducing the  current  to  this  plan,  although  I  would  not  be  understood  as 
limiting  myself  to  its  use.  The  current  of  high  frequency,  therefore,  that  is 
necessary  to  the  successful  working  of  my  invention,  I  produce  by  the  dis- 
ruptive discharge  of  the  accumulated  energy  of  a  condenser  maintained  by 
charging  said  condenser  from  a  suitable  source  and  discharging  it  into  or 
through  a  circuit  under  proper  relations  of  self-induction,  capacity,  resist- 


DESCRIPTIVE. 


47 


ance,  and  period,  in  well -understood  ways.  Such  a  discharge  is  known  to  be, 
under  proper  conditions,  intermittent  or  oscillating  in  character,  and  in  this 
way  a  current  varying  in  strength  at  an  enormously  rapid  rate  may  be  pro- 
duced. Having  produced  in  the  above  manner  a  current  of  excessive  fre- 
quency, I  obtain  from  it  by  means  of  an  induction-coil  enormously  high 
potentials  —  that  is  to  say,  in  the  circuit  through  which  or  into  which  the 
disruptive  discharge  of  the  condenser  takes  place  I  include  the  primary  of 
a  suitable  induction-coil,  and  by  a  secondary  coil  of  much  longer  and  finer 
wire  I  convert  to  currents  of  extremely  high  'potential." 

With  reference  to  the  diagram  Fig.  13. 

"  G  is  the  primary  source  of  current  or  electrical  energy.  I  have  explained 
above  how  various  forms  of  generator  might  be  used  for  this  purpose ;  but 
in  the  present  illustration  I  assume  that  G  is  an  alternating-current  generator 
of  comparatively  low  electromotive  force.  Under  such  circumstances 
I  raise  the  potential  of  the  current 
by  means  of  an  induction-coil  hav- 
ing a  primary  P  and  a  secondary  S. 
Then  by  the  current  developed  in 
this  secondary  I  charge  a  condenser 
C,  and  this  condenser  I  discharge 
through  or  into  a  circuit  A,  having 
an  air-gap  a,  or,  in  general,  means 
for  maintaining  a  disruptive  dis- 
charge. By  the  means  above  de- 
scribed a  current  of  enormous  fre- 
quency is  produced.  My  object  is 
next  to  convert  this  into  a  working- 
circuit  of  very  high  potential,  for 

which  purpose  I  connect  up  in  the  circuit  A  the  primary  P'of  an  induction 
coil  having  a  long  fine  wire  secondary  S'.  The  current  in  the  primary  I" 
develops  in  the  secondary  S'  a  current  or  electrical  effect  of  corresponding 
frequency,  but  of  enormous  difference  of  potential." 

Tesla  has  invented  and  patented  numerous  modifications 
of  apparatus  embodying  these  principles.  One  of  the  fea- 
tures in  his  later  patents,  for  which  great  advantages  are 
claimed,  is  a  series  of  tuned  circuits  of  high  frequency 
exciting  one  another. 


Fig.  13. 


48  WIRELESS   TELEGRAPHY. 

System  of  Concatenated  Tuned  Circuits In  his  patent 

No.  568,178  of  September  22,  1896  (application  filed  June 
20,  1896),  the  inventor  says  in  setting  forth  the  invention: 

"  It  is  well  known  that  every  electric  circuit,  provided  its  ohmic  resistance 
does  not  exceed  certain  definite  limits,  has  a  period  of  vibration  of  its  own 
analogous  to  the  period  of  vibration  of  a  weighted  spring.  In  order  to 
alternately  charge  a  given  circuit  of  this  character  by  periodic  impulses 
impressed  upon  it,  and  to  discharge  it  most  effectively,  the  frequency  of  the 
impressed  impulses  should  bear  a  definite  relation  to  the  frequency  of  vibra- 
tion possessed  by  the  circuit  itself.  Moreover,  for  like  reasons,  the  period 
or  vibration  of  the  discharge-circuit  should  bear  a  similar  relation  to  the 
impressed  impulses  or  the  period  of  the  charging-circuit.  When  the  con- 
ditions are  such  that  the  general  law  of  harmonic  vibrations  is  followed,  the 
circuits  are  said  to  be  in  resonance  or  in  electromagnetic  synchronism,  and 
this  condition  I  have  found  in  my  system  to  be  highly  advantageous. 
Hence,  in  practice,  I  adjust  the  electrical  constants  of  the  circuits  so  that  in 
normal  operation,  this  condition  of  resonance  is  approximately  attained. 

Any  departure  from  this  condition  will  result  in  a  decreased  output,  and 
this  fact  I  take  advantage  of  in  regulating  such  output  by  varying  the  fre- 
quencies of  the  impulses  or  vibrations  in  the  several  circuits. 

Inasmuch  as  the  period  of  any  given  circuit  depends  upon  the  relations 
of  its  resistance,  self  induction,  and  capacity,  a  variation  of  any  one  or  more 
of  these  may  result  in  a  variation  in  its  period.  There  are,  therefore,  vari- 
ous ways  in  which  the  frequences  of  vibration  of  the  several  circuits  in  the 
system  referred  to  may  be  varied,  but  the  most  practicable  and  efficient 
ways  of  accomplishing  the  desired  result,  are  the  following :  (a)  varying  the 
rate  of  the  impressed  impulses  of  current,  or  those  which  are  directed  from 
the  source  of  supply  into  the  charging-circuit,  as  by  varying  the  speed  of  the 
commutator  or  other  circuit-controller;  (b)  varying  the  self-induction  of 
the  charging-circuit ;  (c)  varying  the  self-induction  or  capacity  of  the  dis- 
charge circuit. 

Intensifying  Electric  Oscillations  by  Means  of  Refriger- 
ant. —  Another  suggestion  from  Mr.  Tesla  is  to  employ  as 
a  means  of  increasing  the  intensity  of  electric  oscillations  a 
refrigerant.  He  says  that  "  when  a  circuit  adapted  to 
vibrate  freely  is  maintained  at  a  low  temperature,  the 


THE   TESLA   WIRELESS   PLANT    ON   LONG   ISLAND. 


DESCRIPTIVE.  49 

oscillations  excited  in  the  same  are  to  an  extraordinary 
degree  magnified  and  prolonged,  and  that  he  is  thus  enabled 
to  produce  many  valuable  results  which  have  heretofore 
been  wholly  impracticable  "  The  cooling  agent  may  be 
any  freezing  mixture.  Liquid  air  is  instanced.  In  the 
transmission  of  etheric  waves,  he  would  apply  this  refriger- 
ant to  coils  —  both  at  the  transmitting  and  at  the  receiving 
ends.  He  says  that  the  circuits  at  either  end  of  the  trans- 
mission should  have  the  greatest  possible  self-induction  and 
the  smallest  possible  resistance.  The  invention  is  fully 
described  in  Patent  No.  685,012  of  October  22,  1901. 
(Application  filed  March  21,  1900.) 

Methods  of  Storing  the  Energy  Transmitted,  and  Strength- 
ening Feeble  Impulses.  —  In  another  series  of  patents,  bear- 
ing the  numbers  685,953,  685,954,  686,955,  and  685,956, 
all  granted  in  1901,  Tesla  advances  other  improvements  in 
the  transmission  and  utilization  of  electrical  energy.  The 
fundamental  idea  underlying  these  inventions  is  to  store  the 
energy  transmitted  in  a  condenser  during  any  desired  time 
interval,  and  to  utilize  the  stored  energy,  either  directly  to 
operate  a  receiving  device,  or  to  control  anothef  circuit 
including  the  same.  In  a  modification  of  the  apparatus 
the  latter  circuit  charges  a  condenser,  and  the  impulses 
transmitted  are  used  to  control  the  charge  of  the  con- 
denser. In  order  to  effect  a  charging  by  the  impulses 
conveyed  from  distance,  they  are  commutated  either  by  a 
mechanical  device  or  by  means  of  an  electric  valve  with 
stationary  electrodes.  In  a  special  arrangement  shown,  the 
energy  accumulated  in  the  condenser  is  discharged  through 
the  primary  of  an  induction  coil,  the  secondary  of  which  is 
used  for  the  purpose  of  controlling  the  operation  of  a 


50  WIRELESS    TELEGRAPHY. 

delicate  receiver.  In  this  way  almost  any  degree  of  sensi- 
tiveness which  may  be  desired  can  be  attained.  On  this 
point  the  inventor  says  : 

"  It  will  be  seen  that  by  the  use  of  my  invention  results  hitherto 
unattainable  in  utilizing  disturbances  or  effects  transmitted  through  natural 
media  may  be  readily  attained,  since,  however  great  the  distance  of  such 
transmission,  and  however  feeble  or  attenuated  the  impulses  received, 
enough  energy  may  be  accumulated  from  them  by  storing  up  the 
energy  of  succeeding  impulses  for  a  sufficient  interval  of  time  to  render 
the  sudden  liberation  of  it  highly  effective  in  operating  a  receiver." 

Improved  Mercury  Interrupters.  —  In  order  to  avoid 
waste  of  energy  and  deterioration  of  the  electrodes,  Tesla 
has  designed  a  great  variety  of  mercury  interrupters,  on 
which  he  has  obtained  a  number  of  patents  dated  1897 
and  1898.  In  these  devices  the  circuit  is  made  and  broken 
in  an  hermetically  inclosed  space  and  the  wear  of  the  elec- 
trodes entirely  prevented,  the  contact  surfaces  being  con- 
stituted of  mercury.  In  some  forms  an  inert  gas  under 
great  pressure  is  employed  to  improve  the  action,  the 
inventor  claiming  that  he  has  discovered  that  "a  gas  under 
great  compression  nearly  fulfills  the  ideal  requirements." 

New  Methods  of  Individualization.  —  Instead  of  relying  on 
simple  tuning,  Tesla  has  developed  a  new  principle,  which  is 
set  forth  in  his  last  two  patents  bearing  the  numbers  723,- 
188  and  725,605  (original  application  filed  July  16,  1900). 
In  this  invention  the  transmitter  is  made  to  give  two,  or 
a  greater  number,  of  different  vibrations,  simultaneously  or 
in  a  certain  order  of  succession.  The  receiver  again  has 
a  number  of  tuned  circuits,  each  of  which  responds  to 
one  of  the  vibrations  of  the  transmitter,  and  the  arrange- 
ment is  such  that  only  when  all  the  receiving  circuits  are 


DESCRIPTIVE.  51 

affected  the  indicating  instrument  is  made  to  operate. 
By  the  use  of  this  principle  "  a  degree  of  safety  against 
mutual  and  extraneous  interference  is  attained,  such  as  is 
comparable  to  that  of  a  combination  lock."  On  the  other 
hand,  any  desired  number  of  instruments  can  be  simultane- 
ously operated  through  the  earth  or  other  conducting 
channel.  The  improvement  is  not  limited  to  wireless 
telegraphy.  "  It  will  be  seen,"  says  the  inventor,  "from  a 
consideration  of  the  nature  of  the  method,  that  the  inven- 
tion is  applicable  not  only  in  the  special  manner  described, 
in  which  the  transmission  of  the  impulses  is  effected 
through  the  natural  media,  but  for  the  transmission  of 
energy  for  any  purpose  and  whatever  the  medium  through 
which  the  impulses  are  conveyed." 

Marvelous  Effects  Produced  by  Oscillators  of  Great 
Power.  —  Early  in  1889  Tesla  went  to  Colorado  to  develop 
his  methods  and  apparatus  for  the  transmission  of  wireless 
energy,  and  to  ascertain  the  laws  of  propagation  of  electri- 
cal waves  through  the  earth.  Upon  his  return  he  published 
an  article  which  appeared  in  the  "  Century  "  of  June,  1900, 
in  which  photographic  views  of  some  experiments  with  one 
of  his  oscillators  were  shown.  It  appears  that  with  these 
machines  there  is  no  limit  to  the  intensity  of  the  effects 
and  magnitude  of  the  forces  produced.  According  to  Tesla 
even  interplanetary  space  may  be  bridged  by  the  terrific 
commotions  of  such  an  oscillator.  He  says  : 

"  However  extraordinary  the  results  shown  may  appear,  they  are  but 
trifling  compared  with  those  which  are  attainable  by  apparatus  designed  on 
these  same  principles.  I  have  produced  electrical  discharges,  the  actual 
path  of  which,  from  end  to  end,  was  probably  more  than  one  hundred  feet 
long;  but  it  would  not  be  difficult  to  reach  lengths  one  hundred  times  as 


52  WIRELESS    TELEGRAPHY. 

great.  I  have  produced  electrical  movements  occurring  at  the  rate  of  ap- 
proximately one  hundred  thousand  horse-power,  but  rates  of  one,  five,  or 
ten  million  horse-power  are  easily  practicable.  In  these  experiments  effects 
were  developed  incomparably  greater  than  any  ever  produced  by  human 
agencies,  and  yet  these  results  are  but  an  embryo  of  what  is  to  be. 

That  communication  without  wires  to  any  point  of  the  globe  is  practi- 
cable with  such  apparatus  would  need  no  demonstration,  but  through  a  dis- 
covery which  I  made  I  obtained  absolute  certitude.  Popularly  explained, 
it  is  exactly  this :  When  we  raise  the  voice  and  hear  an  echo  in  reply,  we 
know  that  the  sound  of  the  voice  must  have  reached  a  distant  wall  or 
boundary,  and  must  have  been  reflected  from  the  same.  Exactly  as  the 
sound,  so  an  electrical  wave  is  reflected ;  and  the  same  evidence  which  is 
afforded  by  an  echo  is  offered  by  an  electrical  phenomenon  known  as  a 
"  stationary  "  wave  —  that  is,  a  wave  with  fixed  nodal  and  ventral  regions. 
Instead  of  sending  sound-vibrations  toward  a  distant  wall,  I  have  sent  elec- 
trical vibrations  toward  the  remote  boundaries  of  the  earth,  and  instead  of 
the  wall  the  earth  has  replied.  In  place  of  an  echo  I  have  obtained  a  sta- 
tionary electrical  wave,  —  a  wave  reflected  from  afar. 

Stationary  waves  in  the  earth  mean  something  more  than  mere  tele- 
graphy without  wires  to  any  distance.  They  will  enable  us  to  attain  many 
important  specific  results  impossible  otherwise.  For  instance,  by  their  use 
we  may  produce  at  will,  from  a  sending-station,  an  electrical  effect  in  any 
particular  region  of  the  globe;  we  may  determine  the  relative  position  or 
course  of  a  moving  object,  such  as  a  vessel  at  sea,  the  distance  traversed 
by  the  same,  or  its  speed ;  or  we  may  send  over  the  earth  a  wave  of  elec- 
tricity traveling  at  any  rate  we  desire,  from  the  pace  of  a  turtle  up  to 
lightning  speed." 

One  of  the  experiments  produced  with  a  comparatively 
small  machine  of  this  kind  is  illustrated  in  Fig.  14.  As 
no  person  could  be  anywhere  in  the  vicinity  when  the  dis- 
play is  going  on,  the  picture  was  obtained  by  two  succes- 
sive processes,  the  image  of  Mr.  Tesla's  assistant  being 
taken  at  one  exposure  and  the  electrical  discharges  photo- 
graphed at  another.  Combined  upon  one  plate  they  show 
relative  sizes  of  the  streams  of  light  as  compared  with  a 
human  being.  An  idea  of  the  force  and  volume  of  the 
sparks  may  be  gained  when  it  is  stated  that  the  thick- 


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DESCRIPTIVE.  53 

est  of  them  are  about  23  feet  long,  and  that  a  current  of 
approximately  800  amperes  is  passing  through  the  air. 
The  roar  of  such  a  discharge  can  be  heard  several  miles. 

Since  his  return  from  Colorado  in  1901  Tesla  has  begun 
the  erection  of  commercial  plants ;  but  since  two  years 
nothing  has  been  published  about  his  work.  It  is  under- 
stood that  his  wireless  plant  on  Long  Island  is  nearing 
completion.  A  photographic  view  of  the  same  is  shown  in 
the  illustration  opposite  page  49.  The  structure  presents 
a  curious  appearance.  As  to  the  purpose  for  which  the 
plant  is  designed,  nothing  has,  as  yet,  been  announced  by 
Tesla.  Recently,  however,  the  "  New  York  Sun  "  in  an 
editorial  authorized  by  him,  stated  that  "the  Tesla  oscillator 
will  deliver  to  the  earth  the  shock  that  will  be  felt  and 
recorded  on  its  uttermost  confines." 

Tesla's  Sun-Motors. — Fig.  15  and  16  illustrate  other 
devices  by  the  same  inventor.  These  are  called  "  appara- 
tus for  the  utilization  of  radiant  energy." 

In  Fig.  15,  P  is  a  plate  exposed  to  rays,  and  P'  a  plate 
buried  in  the  ground.  C  is  a  condenser,  the  plates  of 
which  should  present  as  large  a  surface  as  possible,  the 
inventor  having  ascertained  the  amount  of  energy  con- 
veyed to  it  per  unit  of  time  to  be,  under  otherwise  identi- 
cal conditions,  proportioned  to  the  area  exposed  or  nearly 
so.  T  and  T'  are  terminals  of  condenser  C.  Ma  relay 
magnet  or  any  other  device  capable  of  being  actuated  by 
an  electric  current.  </may  be  composed  of  two  very  thin 
conducting  plates  placed  in  close  proximity,  and,  either  by 
reason  of  extreme  flexibility,  or  from  the  character  of 
their  support,  very  mobile. 

It  will  be  seen  that  the  magnet  M,  if   energized    and 


54 


WIRELESS   TELEGRAPHY. 


de-energized,  will  actuate  armature  a,  and,  with  a  pawl  and 
ratchet  movement,  turn,  one  step  at  a  time,  the  wheel  W. 
When  the  condenser  C  is  charged  to  a  certain  potential 
the  dielectric  between  the  strips  will  break  down,  and  the 
condenser  discharge  its  accumulated  energy  through  mag- 
net M.  When  the  strain  on  the  dielectric  has  been  re- 
lieved the  strips  t  tr  will  resume  their  normal  position. 

The  originator  of  this  device  says  that  "many  useful 
applications  of  utilizing  the  radiations  emanating  from  the 
sun,  and  many  ways  of  carrying  out  the  same,  will  at  once 
suggest  themselves." 


Application  of  Preceding  to  Telegraphy.  —  The  applica- 
tion of  this  invention  to  telegraphy  is  suggested  in  Fig.  16, 
in  which  the  source  S  of  rays  is  a  "  Roentgen  tube  having 
but  one  terminal  k,  generally  of  aluminum,  in  the  form  of 
half  a  sphere  with  a  plane  polished  surface  on  the  front 
side  from  which  the  rays  are  thrown  off."  Interruption 
of  the  generation  of  the  rays  at  differing  intervals  may 


DESCRIPTIVE. 


55 


serve  to  produce  long  or  short   signals   on  the  relay    R. 
The  it'  of  Fig.  15  takes,  in  Fig.  16,  the  form  of  a  brush 


A"1* 


^         Inventor 


Fig.  16. 


and    segmented    wheel.     The    condenser    discharges    are 
stepped  to  higher  intensities  through  induction  coil,  /  s. 


56  WIRELESS    TELEGRAPHY. 


METHODS    OF    DR.    SLABY. 

In  Mr.  Kerr's  work  on  Wireless  Telegraphy  is  a  foot- 
note* to  the  effect  that  Dr.  Slaby  of  Charlottenburg,  Ger- 
many, was  present  with  Mr.  Preece  in  the  latter's  Bristol 
Channel  experiments,  and  had  repeated  them  before  the 
Emperor  of  Germany  at  Berlin.  Presumably  this  refers 
to  the  tests  of  1892.  Mr.  Fahie  has  recorded  that  Dr. 
Slaby  was  also  present  at  a  Bristol  Channel  experiment 
made  by  Marconi  on  May  I3th,  1899  ;  and  it  seems  to  be 
the  opinion  of  the  English  writers  that  Dr.  Slaby's  suc- 
cessful trials  in  etheric  transmission  were  all  subsequent 
to  this  latter  visit  to  England. 

Controversy  Between  Slaby  and  Marconi.  —  In  a  lecture 
before  the  English  Society  of  Arts  delivered  May  1 5th, 
1901,  Marconi  quotes  from  a  paper  read  by  Slaby  in 
December,  1900,  in  which  the  latter,  referring  to  the  Mar- 
coni system,  said :  "  The  receiving  wire  was  suspended, 
insulated,  and  attached  at  the  end  of  the  coherer,  the 
other  pole  of  which  was  connected  to  earth."  Marconi,  in 
controverting  this  point,  contended  that  in  one  of  his 
British  patents,  application  for  which  was  made  on  June  I, 
1898,  or  two  and  one-half  years  previous  to  Slaby's  state- 
ment, he  (Marconi)  said  of  his  own  device,  " according 
to  this  invention  the  conductor  ( aerial )  is  no  longer 
insulated,  but  is  connected  to  earth  through  the  pri- 
mary of  an  induction  coil,  while  the  ends  of  the  imper- 
fect contact,  or  coherer,  are  connected  to  the  ends  of 
the  secondary  of  the  connections  passing  through  the 
coherer." 


DESCRIPTIVE. 


57 


Slaby's  Multiplier.  —  Slaby  has  applied  to  his  apparatus 
a  coil  of  wire,  designated  a  multiplier,  which  he  claims 
acts  as  a  resonator,  being  analogous  to  a  hollow  box  placed 
under  a  tuning-fork.  The  Slaby  adherents  are  careful  to 
state  that  this  device  should  not  be  confounded  with  an 
induction  coil.  Marconi,  however,  in  the  same  paper 
before  the  Society  of  Arts,  previously  quoted,  points  out 
that  it  is  no  new  thing  to  use  a  single  coil  of  wire  to 
produce  self-induction. 

Slaby's  Achievements.  —  Immediately  upon  his  return 
from .  England  in  May,  1 899,  after  his  attendance  at  the 
tests  of  the  young  Italian  inventor,  Dr.  Slaby  succeeded 
with  his  own  apparatus  in  transmitting  signals  a  distance 
of  about  thirteen  miles ;  and  it  has  been  claimed  for  him, 
although  doubted  by  the  friends  of  Marconi,  that  he  has 
covered  ninety  miles  from  the  shore  to  a  moving  vessel  at 
sea.  The  German  electrical  papers  say  that  in  competi- 
tive tests  the  superiority  of  the  German  system  has  been 
to  them  satisfactorily  proved  ;  but  the  Marconi  adherents, 
properly  enough,  contend  that  a  more  convincing  test  of 
comparative  merit  might  be  had  if  each  side  were  allowed 
to  handle  its  own  apparatus.  In  a  newspaper  interview  in 
October,  1902,  Marconi  is  reported  as  saying  of  Slaby, 
"  He  has  adopted  the  main  features  of  my  system,  the 
vertical  wire,  for  instance.  He  introduces  other  variations 
which  I  consider  detrimental.  He  has  established  a  so- 
called  system  by  which  he  has  covered  one-twentieth  of 
the  distance  I  have  covered." 

No  United  States  Patents  to  Slaby Up  to  this  writing 

it  has  not  been  possible  to  find  any  American  patent  of 


58  WIRELESS   TELEGRAPHY. 

the  German  scientist,  but  it  is  rumored  that  he  has  as- 
signed American  rights  under  his  inventions  to  the  Gen- 
eral Electric  Company  of  Germany. 

The  Slaby  Theory.  —  Dr.  Slaby  has  built  his  system  on 
the  theory  that  if  by  means  of  a  spark  producer  at  its 
lower  end  electrical  oscillations  are  set  up  in  a  vertical 
wire,  the  maximum  amplitude  of  each  oscillation  will  be  at 
the  top  point  of  the  high  wire. 

Fig.  17  is  a  diagrammatic  representation  of  one  com- 
plete wave  A  E.  At  B  is  its  greatest  rise,  or  its  "crest." 


Fig.  17. 

At  D  its  point  of  extreme  depression.  A,  C,  and  E  are 
neutral  points  called  nodes.  It  follows,  according  to  Dr. 
Slaby,  that  a  full  wave  from  a  transmitting  station  will  be 
just  four  times  the  length  of  the  vertical  wire  which  is  set 
in  oscillation  by  the  spark ;  and  also  that  if  the  antenna 
of  the  receiver  be  put  to  earth  its  vibration  will  produce  a 
crest  at  its  top  corresponding  to  B,  Fig.  17  ;  and  that  in 
consequence  at  the  point  of  connection  with  the  earth  will 
be  nodes  such  as  are  indicated  in  Fig.  17,  at  A  and  C 
and  E. 

Now,  if  a  wire  be  carried,  as  in  Fig.  18,  from  the  node 
A,  the  wave  motion,  of  which  B  is  the  crest,  will  be  prop- 


DESCRIPTIVE. 


59 


agated  along  the  wire  A  F,  and  provided  the  wire  A  F  is 
of  exactly  the  same  length  as  the  wire  A  G,  the  crest  B' 
of  the  new  wave  will  be  formed  at  F,  the  point  at  which 
Dr.  Slaby  attaches  his  coherer.  He  claims  by  this  scheme 
of  connections  that  transmitted  waves  always  affect  the 
coherer  when  at  their  maximums  of  potential.  It  is  said 
that  those  waves  for  which  the  earthed  point  A  is  not  a 
node  will  fail  to  be  propagated  along  the  wire  A  F,  but 


) 


Fig.   18. 

will  be  conducted  directly  into  the  ground,  with  the  result 
that  only  waves  of  a  predetermined  period  will  affect  the 
coherer,  thus  guarding  against  interception  or  interference ; 
or,  again,  that  a  number  of  differently  constituted  receiving 
conductors,  each  adapted  to  receive  an  especial  kind  of 
wave,  may  be  branched  from  one  receiving  antenna,  thus 
making  a  wireless  multiplex.  There  are,  however,  so  far 


60  WIRELESS   TELEGRAPHY. 

as  is  known,  no  published  results  as  to  the  number  of  cir- 
cuits that  may  thus  be  operated,  or  the  distance  over  which 
signals  in  groups  may  be  transmitted. 

Application  of  Multiplier.  —  While  the  author  has  not 
seen  the  application  of  the  "multiplier"  clearly  shown,  it 
may  be  assumed  that  the  lower  part  of  the  antenna  itself 
is  in  the  form  of  a  coil ;  that  the  path  to  the  coherer,  which 
must  equal  in  length  the  antenna,  is  also  in  the  form  of  a 
coil,  but  that  these  two  coils  are  separate,  and  that  there  is 
between  them  no  inductive  action. 

Slaby  Coherer.  —  As  a  receiving  device,  Dr.  Slaby  uses 
steel  balls  lying  loosely  between  aluminum  plates.  It  is 
claimed,  on  the  one  hand,  that  this  instrument  is  much 
more  sensitive  than  the  ordinary  forms  of  what  are  called 
"  permanent  "  coherers,  such  as  tubes  of  carbon  dust,  but 
admitted  on  the  other  that  it  is  not  so  sensitive  as  a  deli- 
cately adjusted  silver  coherer;  not,  therefore,  so  well  suited 
to  extreme  long  distance  transmission ;  and  that  it  is  not 
sufficiently  diverse  in  its  resistances  to  allow  of  working  a 
relay ;  and  consequently  that  a  recording  instrument  which 
requires  for  its  operation  the  local  circuit  of  a  relay  cannot 
be  used.  To  restate  the  advantages  of  the  steel  and  alu- 
minum coherer,  it  is  the  most  sensitive  form  of  "self-right- 
ing "  coherer ;  and  such  being  the  case  is  best  adapted  of 
any  to  work  at  moderate  distances  where  the  signaling 
does  not  require  a  permanent  record.  The  operator  need 
have  no  difficulty  in  reading  by  sound  from  a  telephone 
receiver,  and  can  work  faster  than  with  an  ink-marker  ; 
and  any  system  which  eliminates  the  tapper  does  away 
with  a  complicated  and  troublesome  mechanism.  The 


DESCRIPTIVE. 


6l 


Slaby  receiver  is  apparently  much  easier  of  adjustment 
than  can  be  any  non-restoring  coherer. 

Dr.  Slaby's  circuits  have  inductances  and  capacities  both 
at  the  transmitting  and  receiving  ends.  When  he  essays 
transatlantic  signaling  he 
will  probably  use  a  silver 
coherer.  Then  he  may 
tune  by  getting  the  same 
product  value  in  the  com- 
bination of  capacity  and 
induction  at  each  end  of 
the  transmission.  Mar- 
coni does  the  same. 
Slaby's  connections  are 
somewhat  different  from 
those  of  his  principal  rival, 
but  whether  his  net  re- 
sults will  be  greater  re- 
mains for  actual  tests  to 
determine. 

Mr.  Collinses  Descrip- 
tion of  Slaby  System — 

In    the  Scientific  Ameri- 
can  of    December    28th,  r===  E 
1901,  is  an  article  by  Mr.  Fig  1Q< 

A.  F.  Collins  which  gives 

a  number  of  diagrams  of  Dr.  Slaby's  plans  of  connections, 
two  of  which,  with  a  brief  description,  are  by  permission 
reproduced. 

Referring  to  Figs.  19  and  20,  D  is  the  coherer  (consist- 
ing of  steel  balls  between  aluminum  plates).      In  Fig.  19 


62 


WIRELESS    TELEGRAPHY. 


the  path  to  ground  from  antenna  A  by  way  of  coil  L"'  is 
in  shunt  with  the  coil  L",  and  both  are  in  shunt  with  the 
key  K',  which  while  the  operator  is  transmitting  is  kept 
closed  to  protect  the  coherer  from  strong  waves.  Induct- 
ance coil  L,  Fig.  19,  is  in  tune  with  antenna  A,  and  also 
in  accord  with  waves  from  the  distant  station  (see  Fig.  20). 


Kite 


Fig.    20. 


It  is  regulated  by  the  adjustments  of  induction  L'"  and 
capacity  C'.  The  method  of  changing  the  value  of  C'  is 
shown  by  the  position  of  switch-arm  F  and  connections  at 
m,  n  and  o.  Battery  B'  may  be  one  dry  cell ;  L"  acts  as 
a  choking  coil.  Fig.  20  represents  the  transmitting  appa- 
ratus of  Dr.  Slaby,  in  which  M  is  a  multiplier  and  A  with 
its  terminating  kite  the  wave-gate. 


DESCRIPTIVE.  63 


THE    LODGE    SYSTEM. 

Fig.  21  is  arranged  as  a  typical  diagram  of  Professor 
Lodge's  ethereal  transmitter.  In  the  Lodge  nomenclature 
it  is  called  a  "  radiator."  Three  spark-gaps  are  in  the  series, 
viz.:  the  "  starting,"  the  "supply,"  and  the  "discharge." 
It  is  the  assertion  of  the  designer  that  by  this  multiplicity 
of  gaps  the  oscillations  are  made  more  "persistent,"  i.e., 
not  so  soon  "damped."  He  says  that  charges  so  com- 
municated are  left  to  oscillate  free  from  any  disturbance 
due  to  maintained  connection  with  the  source  of  electricity ; 
and  therefore  "  oscillate  longer  and  more  freely  than  when 
supplied  by  wires  in  the  usual  way."  Another  advantage 
is  that  the  same  emitter,  inductance  coils,  and  earth  con- 
nection may  conveniently  be  used  as  a  part  of  the  receiving 
apparatus.  It  will  be  seen  that  at  the  supply  knobs  the 
Ruhmkorff  coil  is  always  in  absolute  disconnection  from 
the  final  discharge  circuit.  If  now  the  receiving  circuit 
shown  in  Figs.  22  or  23  be  attached,  as  indicated  by  the 
dotted  lines  X  X  in  Fig.  21  and  the  solid  lines  xx  in  Figs. 
22  and  23,  and  at  the  same  time  the  discharge  break  be 
bridged  out  of  circuit  by  a  good  conductor  across  it,  the 
apparatus  is  ready  for  use  as  a  receiver.  The  connections 
may  be  so  arranged  that  one  movement  of  a  knife  switch 
will  change  the  device  from  transmitter  to  receiver,  or,  as 
the  inventor  would  say,  from  "  radiator  to  resonator." 

Inductance  Coils.  —  Fig.  24  shows  the  inductance  coil 
of  the  receiver  surrounded  by  a  secondary  winding,  the 
two  coils  forming  a  step-up  transformer  to  raise  the  poten- 
tial of  waves  from  a  distant  source. 


64 


WIRELESS   TELEGRAPHY. 


THIN  WIRE  INDUCTANCE  COII. 

Fig.  21. 


CAPACITY  AREA  =  EARTH 


Fig.  24. 


DESCRIPTIVE. 


Capacity  Areas.  —  Fig.  25  represents  the  form  preferred 
by  Professor  Lodge  for  "  capacity  areas,"  "  diverging  cones 
with  vertices  adjoining  and  their  larger  areas  spreading 
out  into  space."  He 
says  that  this  form  com- 
bines low  resistance  with 
great  electrostatic  ca- 
pacity.1 

Supply    Gap.  —  The 

action  of  the  "supply 
gap"  is  to  cause  to  be 
stored  upon  the  "  supply 
knob  "  a  charge  of  elec- 
tricity that  is  sufficiently  powerful  to  cross  the  air  space. 
A  condenser  is  a  similar  storage  of  power,  and  supposedly 
much  easier  of  exact  adjustment. 

In  Professor  Lodge's  device  there  is  in  the  local  cir- 
cuit as  here  shown  no  condenser,  such  as  is  found  in  the 
Marconi  or  Tesla  systems,  to  build  up  the  feeble  waves  ar- 
riving at  the  receiving  end  of  a  long  distance  transmission  ; 
nor  are  there  any  choking  coils  to  prevent  the  dissipation 
over  the  relay  circuit  of  the  charge  that  affects  the 
coherer.1 

1  See  Fig.  68,  p.  177,  Part  IV. 


Fig.  25. 


66  WIRELESS   TELEGRAPHY. 


WORK    OF    UNITED    STATES    WEATHER   BUREAU. 

Engagement  of  Specialist.— The  United  States  Weather 
Bureau  began,  early  in  1900,  a  systematic  course  of  experi- 
mentation in  Wireless  Telegraphy,  employing  Professor 
Reginald  A.  Fessenden  as  a  specialist.  In  a  paper  written 
by  him  in  1902,  it  was  asserted  that  important  advances  had 
been  made,  one  of  which  was  overcoming  largely  the  loss 
of  energy  experienced  in  other  systems.  He  also  declared 
that  syntony  was  not  safely  selecting,  but  that  he  had 
discovered  several  methods  which  were.  The  following 
extract  from  the  Fifth  Annual  Report  of  the  Secretary 
of  Agriculture  is  a  generalization  of  the  Government 
work  up  to  the  year  1901  : 

"  While  there  is  much  experimental  work  yet  to  be  done  before  the 
present  system  is  reliable  for  intership  communication,  or  before  any  two 
systems  can  work  within  the  same  field  without  each  rendering  the  other 
useless,  such  progress  has  been  made  by  the  government  experimenters 
that,  with  no  interference  by  private  systems,  stations  can  be  successfully 
operated  over  at  least  one  hundred  and  fifty  miles  of  coast  line ;  and  they 
are  now  in  operation  on  the  North  Carolina  and  Virginia  coasts,  and  soon 
will  be  instituted  between  the  Farallone  Islands  and  the  mainland,  and 
Tatoosh  Island  and  the  mainland,  on  the  Pacific  coast." 

Experimental  Stations  of  U.  S.  Government.  —  Early  in 
1901  the  Weather  Bureau  official  installed  Mr.  Fessenden 
at  Wier's  Point,  Roanoke  Island,  North  Carolina  ;  and  he 
has  since  made  experimental  transmissions  across  water  to 
a  station  located  about  five  miles  west  of  Cape  Hatteras, 
the  distance  between  the  two  stations  being  almost  exactly 
fifty  miles.  The  following  letters  from  the  Weather 
Bureau  staff  have  been  given  to  the  public  : 


DESCRIPTIVE.  67 

MANTEO,  ROANOKE  ISLAND,  N.C., 

April  4,  1902. 
CHIEF  UNITED  STATES  WEATHER  BUREAU, 

Washington,  D.C.: 

After  working  with  Professor  Fessenden's  new  receiver,  between 
Hatteras  and  Roanoke,  I  would  report  as  follows  : 

The  receiver  is  positive  in  its  action,  and  entirely  and  absolutely  reliable. 
It  is  entirely  different  in  nature  and  action  from  the  coherer,  and  gives  no 
false  signals  like  the  latter  does. 

I  could  get  every  single  dot  and  dash  made  at  Hatteras  with  the  utmost 
clearness,  and  can  receive  with  it  at  the  same  rate  of  speed  as  over  an 
ordinary  telegraph  line.  It  is  possible  for  any  expert  telegrapher  to  receive 
by  it  as  fast  as  the  key  can  be  handled. 

I  have  had  no  trouble  in  using  the  receiver  except  that  due  to  bad 
sending  at  the  other  end,  and  even  then  could  make  out  every  single  dot 
and  dash,  but  could  not  read  them. 

The  signals  and  messages  were  taken  perfectly  on  the  new  receiver 
when,  under  the  same  conditions  and  connections,  the  coherer  was  tried 
and  would  not  give  a  single  dot. 

Yours  respectfully,  Louis  DORMAN, 

Observer,  Weather  Bureau, 

MANTEO,  ROANOKE  ISLAND,  N.C., 

Professor  REGINALD  A.  FESSENDEN  : 

I  would  report  that  in  the  test  made  by  Mr.  Dorman,  the  following  is  a 
comparison  of  the  amount  of  energy  necessary  to  work  the  standard  co- 
herer and  the  receiver  used  by  Mr.  Dorman  in  the  test  referred  to  in  his 
report : 

Taken  as  our  standard  coherer  one  working  well  —  i.e.,  giving  good 
clear  transmission  of  messages  when  attached  to  a  single  No.  18  wire  five 
feet  long,  the  sending  wire  being  similar  and  of  the  same  length,  the  spark- 
gap  being  one-eighth  inch  between  slightly  rounded  points,  and  obtained 
from  a  coil  capable  of  giving  three-sixteenths  inch  spark  between  points 
when  the  distance  between  sending  and  receiving  wires  is  forty-five  feet,  and 
both  coherer  and  coil  are  resting  on  the  surface  of  the  ground  —  then  the 
third  message  received  by  Mr.  Dorman  in  the  tests  referred  to  in  his  report 
was  received  with  one  five-hundred-and-seventy-sixth  of  the  least  amount 
of  energy  required  to  work  the  standard  coherer  over  the  same  distance, 
and  with  the  same  vertical  and  receiving  wires  used  in  each  case,  and  with 
the  coherer  worked  with  a  transformer  with  maximum  efficiency  ratio  of 

transformation  and  circuit  accurately  tuned. 

A.  H.  THIESSEN,  Assistant. 


68  WIRELESS  TELEGRAPHY. 

Upon  April  27,  1902,  a  series  of  tests  were  made  from 
the  Roanoke  station  before  various  Government  officials, 
resulting  in  good  transmission  over  fifty  miles  of  a  surface 
partly  sea  water  and  partly  fresh  water. 

U.  S.  Government  Opens  Proposals  For  Wireless  Tele- 
graph in  Alaska.  — Upon  May  6th,  1902,  the  Chief  Signal 
Officer  of  the  Weather  Bureau  opened  proposals  for  estab- 
lishing wireless  telegraph  systems  in  Alaska,  over  four 
different  routes,  as  follows  : 

A.  Between    Fort    Davis   and    some   point   on    Strait 
Island,  a  distance  of  ninety  nautical  miles. 

B.  Between    Fort    Davis   and    Fort    St.   Michael's,  a 
distance  of  one  hundred  and  eight  miles. 

C.  From  Rampart  City  to   Winter  Hours,  a  distance 
of  one  hundred  and  thirty-she  miles. 

D.  From  Fort  Gibbon  to  a  point  near  Bates  Rapids  in 
the  Tanana  River,  an  air-line  distance  of  one  hundred  and 
sixty-five  miles. 

The  bidders  were,  Queen  and  Company  of  Philadelphia 
representing  the  Fessenden  Apparatus ;  The  Marconi 
Company  of  England ;  the  owners  of  the  Arco-Slaby 
system  in  Germany  ;  the  American  Wireless  Telephone 
and  Telegraph  Co.  of  Philadelphia ;  Foote,  Pierson  &  Co.  ; 
the  DeForest  Wireless  Telegraph  Company. 

The  proposals  of  the  last  four  bidders  were  not  con- 
sidered, for  the  reason  that  they  would  not  agree  to 
install  and  work  their  systems  for  ten  days  prior  to  accept- 
ance by  the  Government.  Contracts  were  finally  made 
with  Queen  and  Company  for  the  B  route,  one  hundred 
and  eight  miles,  with  a  rate  of  transmission  guaranteed  to 
be  not  less  than  twenty-five  words  per  minute ;  with  the 


DESCRIPTIVE.  69 

Marconi  Company  for  the  D  route,  one  hundred  and  sixty- 
five  miles,  with  a  guaranteed  speed  of  twelve  words  per 
minute. 

The  Marconi  Company  departed  from  the  specifications 
to  the  extent  of  demanding  a  royalty  after  the  first  year  of 
$250  per  annum  upon  each  set  of  instruments;  and  also 
demanding  one-half  of  any  receipts  for  commercial  tele- 
graphy which  might  be  received  by  the  Government. 

In  accepting  the  contracts,  both  companies  have  agreed 
that  unless  their  systems  shall  work  every  day  without 
interruption  the  Government  shall  be  exempt  from  pay- 
ment. It  was  thought  that  both  installations  would  be  in 
working  order  by  October,  1902. 

Interview  with  Mr.  Fessenden.  —  In  an  interview  with 
a  New  York  Journal  correspondent,  Mr.  Fessenden  said 
of  his  apparatus  that  he  did  not  use  any  air  transformer 
at  the  sending  end  ;  nor  concentric  cylinder  for  emitters 
and  antennae,  such  as  were  employed  by  the  Marconi 
Company ;  that  he  used  capacity,  but  that  it  was  arranged 
in  a  manner  entirely  different  from  that  in  other  systems  ; 
that  he  did  not  employ  a  coherer  or  any  form  of  imperfect 
contact  ;  that  his  apparatus  was  of  solid  metal,  and  acted 
under  a  physical  law  entirely  different  from  that  which 
governs  the  receiving  devices  of  Marconi.  While  the 
telephone  was  used  as  a  recorder  of  signals,  he  said  he 
could  also  get  good  service  from  a  siphon  recorder.  He 
asserted  that  he  had  paid  particular  attention  to  selective 
and  multiplex  systems,  and  was  well  satisfied  with  the 
results  in  that  direction.  He  believed  that  when  a  system 
of  machine  receiving  was  perfected  it  would  be  possible  to 
transmit  five  hundred  words  per  minute. 


;o  WIRELESS   TELEGRAPHY. 

Lieutenant  Beecher's  Paper  Before  American  Institute.  — 
On  May  28th,  Lieutenant  Beecher  of  the  United  States 
Navy,  who  had  been  investigating  the  Fessenden  system, 
read  a  paper  before  the  American  Institute  of  Electrical 
Engineers,  in  which  he  said  that  in  some  respects  the  Fes- 
senden apparatus  was  more  reliable  than  that  devised  by 
other  inventors.  He  emphasized  the  fact  that  one  defect 
of  a  telephonic  receiving  apparatus  is  the  need  of  an 
efficient  calling-up  signal  ;  and  suggested  that  a  coherer 
might  be  used  to  receive  the  calling  signal,  and  be  after- 
ward switched  out  and  replaced  by  a  telephone  receiver. 


DESCRIPTIVE.  71 


PATENTS    ISSUED    TO    PROFESSOR    FESSENDEN. 

On  August  1 2th,  1902,  there  were  issued  to  Mr.  Fes- 
senden  thirteen  patents  on  various  methods,  devices,  and 
systems  for  signaling  without  wires.1 

The  First  Two  Patents.  —  In  the  first  two  patents  of 
the  series  it  is  indicated  that  it  was  Mr.  Fessenden's  inten- 
tion to  devise  a  signaling  system  which  would,  be  more 
positive  in  its  action  at  moderate  distances  than  was  the 
only  receiving  instrument  known  at  that  time,  the  coherer. 
He  designated  the  transmitted  vibrations  which  affect  a 
coherer  as  "voltages,"  meaning  electric  currents  of  high 
potential  in  contradistinction  to  the  "  currents"  of  compar- 
atively low  potential  which  he  employed. 

His  receiving  organization  is  a  tuned  circuit  which  is 
always  closed,  and  is  thus  differentiated  from  a  coherer 
which  may  be  called  a  normally  open  circuit.  Hence  his 
receiver  is  always  receptive,  always  capable  of  being  affected 
by  waves ;  whereas  for  a  portion  of  the  time  during  which 
signals  are  being  sent,  the  coherer  is  incapable  of  response. 
Another  distinctive  feature  is  the  fact  that  the  indications 
produced  by  the  Fessenden  receiving  mechanism  are  de- 
pendent upon  the  total  amount  of  energy  emitted  to  form 
a  signal,  and  not,  as  in  the  case  of  a  coherer,  dependent 
upon  the  maximum  of  the  voltage. 

In  the  description  of  that  first  invention  it  is  explained 
that  a  single  electromagnetic  wave  of  the  type  used  by  the 
inventor  "will  have  produced  its  impulses  before  the  re- 
ceiver employed  will  have  made  an  appreciable  motion  "  ; 

1  Many  of  these  devices  are  described  as  "  Apparatus"  in  Part  IV.,  and  a  full  list  of 
them  is  a  portion  of  Part  II.,  under  "  Inventors  and  Inventions." 


72  WIRELESS    TELEGRAPHY. 

but  by  using  a  source  of  sustained  radiation  at  the  sending 
end  the  effect  of  the  waves  is  cumulative  ;  and  since  the 
receiver  is  constantly  receptive,  the  effects  added  together 
from  a  number  of  waves  serve  to  produce  appreciable  in- 
dications. Repeating  the  foregoing  statements  in  other 
words,  the  appliances  are  adapted  to  produce  at  the  send- 
ing station  electromagnetic  waves  of  comparatively  low 
frequency  and  low  potential,  but  to  sustain  as  much  as  pos- 
sible the  oscillations  from  each  impulse,  and  at  the  receiv- 
ing station  to  use  a  wave-responsive-device  upon  a  closed 
circuit  tuned  to  the  same  frequency  as  the  sending  organi- 
zation, which  would  be  sufficiently  affected  by  the  cumula- 
tive effect  of  a  number  of  waves  as  to  produce  observable 
mechanical  movements. 

After  the  declarations  of  principles,  which  constitute 
considerable  portions  of  his  first  two  patents,  there  ap- 
peared in  successive  inventions  two  different  forms  of  radi- 
ating wave-gates.1 

Third  Patent  for  a  "  System. "  —  Next  in  order  is  a 
"system."  Its  objects  are  to  provide  suitable  means  for 

raising  the  voltage 
at  the  receiving 
station  by  a  trans- 
former ;  to  increase 
the  number  of  os- 
cillations in  the 
sending  conductor 
during  its  discharg- 
ing period  ;  and  to  improve  localization  by  so  tuning  the 
receiving  apparatus  that  it  will  respond  solely  to  waves 


See  detailed  description  in  Part  IV. 


DESCRIPTIVE.  73 

of  one  periodicity.  Referring  to  Fig.  26,  the  inventor 
says  that  a  feature  (indicated  at  6)  is  the  addition  of  a 
capacity  to  the  sending  conductor  in  connection  with 
a  transformer  at  the  receiving  station  for  raising  the  volt- 
age in  the  secondary  circuit  ;  that  another  feature  is  the 
capacity  (8)  placed  in  shunt  with  the  coherer  (9)  ;  still 
another,  an  opposing  source  of  voltage  (12-11)  bridged 
across  the  secondary  circuit  and  presenting  a  counter  elec- 
tromotive force  to  the  local  battery  while  the  coherer  is  in 
operation.  The  PRINCIPAL  ADVANTAGE  claimed  seems  to 
be  the  improvement  in  selection,  due  to  the  use  of  a  plu- 
rality Of  TUNED  CIRCUITS. 

Quoting  the  inventor's  own  words  : 

Waves  of   One  Periodicity  Subject  to  Interference.  — 

On  account  of  the  fact  that  it  is  preferable  to  use  sending 
conductors  having  large  capacity,  or  large  capacity  and 
self-induction,  and  that  in  these  cases  the  curve  of  reso- 
nance is  broadened,  it  has  heretofore  been  impossible  to 
make  the  receivers  respond  solely  to  waves  of  one  periodi- 
city, as  other  periodicities,  if  above  a  certain  power,  will 
affect  the  receivers. 

Perfect  Resonance  Attained  by  Plurality  of  Conduc- 
tors. —  By  constructing  the  sending  conductor  so  the  oscil- 
lations for  each  total  discharge  are  increased,  and  by 
employing  at  the  receiving  station  two  or  more  tuned  cir- 
cuits, a  very  perfect  resonance  or  tuning  between  the 
stations  can  be  attained. 

Effects  from  One-Tuned  Circuit  and  Two-Tuned  Cir- 
cuits. —  With  a  one-tuned  circuit  at  the  receiving  station 
and  with  sending  conductors  permitting  a  rapid  radiation 


74 


WIRELESS    TELEGRAPHY. 


at  the  sending  station,  electrostatic  and  hysteresis  effects 
become  very  prominent,  and  the  great  self-inductance 
desirable  for  sharp  resonance  cannot  be  attained.  By 
employing  at  the  receiving  end  two  tuned  circuits,  the  first 
consisting  of  the  receiving  conductor  and  the  other  second- 
ary to  the  first,  the  relative  inductance  may  be  greater  in 
the  secondary  than  in  the  primary  circuit  of  the  receiv- 
ing conductor  or  the  sending  conductor,  in  which  latter, 
as  before  explained,  the  capacity 
is  preferably  a  dominant  factor  of 
tuning,  and  the  electrical  effect  in 
the  secondary  will  occur  only  when 
the  periods  are  very  closely  the 
same. 

An  Invention  in  Wireless  Teleph- 
ony  In  an  application  for  a  patent 

filed  September  28th,  1901,  part  of 
the  subject  matter  had  reference  to 
telephoning  without  wires.  The 
method  is  illustrated  in  Fig.  27,  in 
which  9  is  a  transmitting  telephone  modifying  by  means 
of  battery  8,  coil  7  and  core  3,  the  impulses  imparted  to 
wave-gate  I. 

Invention  for  Localization  of  Signals.  —  An  arrange- 
ment for  the  more  distinct  localization  of  signals  than  can 
be  obtained  from  one  set  of  tuned  apparatus  is  shown  in 
Fig.  28,  in  which  ia  and  2a  are  emitting  wave-gates  tuned 
to  different  periodicities,  and  6a  and  7a  are  receiving  anten- 
nae respectively  corresponding  in  frequency  to  ia  and 
2a,  and  consequently  the  armature  16  which  represents  the 


Fig.  27. 


DESCRIPTIVE. 


75 


means  for  mechanical  movement  at  the  receiving  station 
responds  "only  to  the  combined  action  of  waves  or  im- 
pulses corresponding  in  period  and  in  other  characteristics 
to  those  generated  "  by  the  combined  action  of  ia  and  2a. 


Fig.  28. 

Reference  is  made  to  Part  IV.,  wherein  are  described 
inventions  by  Mr.  Fessenden  of, 

1.  Means  "  to  provide  for  the  MAINTENANCE  of  a  CERTAIN 

DEFINITE  RELATION  BETWEEN  the  RESISTANCE  and  CAPA- 
CITY of  the  sending  mechanism,  regardless  of  the  POTEN- 
TIAL employed. 

2.  A  WAVE-RESPONSIVE-DEVICE,  consisting  of  a  conductor 
having  small  heat  capacity  and  low  resistance. 

3.  An  appliance  adapted  to  make  a  highly  CONDUCTIVE 
WAVE  PATH  OVER  THE  EARTH  for  some  distance,  from  the 
sending  end  and  receiving  wave-gates  respectively.     This 
is  denominated  by  the  inventor  a  "  wave-chute." 

4.  An  arrangement  for  PRODUCING  VISIBLE  INTERPRET- 
ABLE  CHARACTERS  on  a  strip  or  film   by  a  PHOTOGRAPHIC 
process,  and  for  developing  and  fixing  the  same. 

Fessenden's  Selective  System.  —  Another  invention  is  a 
system  of  selection  whereby  each  of  a  number  of  stations 


76  WIRELESS    TELEGRAPHY. 

has  a  tune  or  period  of  resonance  proper  to  itself,  as  each 
Western  Union  Telegraph  station  has,  where  several 
stations  work  upon  one  wire,  its  particular  letter  or  com- 
bination of  letters  for  a  "call."  In  this  system,  part  of 
the  sending  mechanism  is  a  key,1  constructed  with  a  num- 
ber of  different  contacts  which  are  the  terminals  of  differ- 
ently tuned  circuits.  The  connections  are  normally  made 
so  that  their  period  of  resonance  is  that  allotted  to  each 
station  ;  but  any  station  may  call  and  exchange  signals 
with  any  other  station  by  first  putting  itself  in  resonance 
with  the  one  with  which  it  desired  to  communicate. 


Fessenden  Signaling  System  of  July,  1902  (Fig.  29).  — 
For  the  Fessenden  patent  No.  706,745,  application  was 
made  July  i,  1902.  It  is  for  a  "system,"  apparently  the 
final  result  of  the  researches  and  experiments  made  by  the 
inventor  for  the  Government.  The  drawings  of  the  patent 
comprise  five  illustrations,  the  second,  third,  fourth,  and 
fifth  figures  being  forms  of  apparatus  at  the  receiving  sta- 
tion which  are  modifications  of  that  shown  in  the  first  fig- 
ure. As  it  is  presumable  that  the  initial  illustration  is  the 
preferred  one,  it  has  been  selected  for  description,  and  re- 
produced here  as  Fig.  29. 

Transmitter.  —  Quoting  from  the  patent  specification, 
"The  form  of  apparatus  shown  in  Fig.  29  consists  at  the 
sending  station  of  a  radiating  conductor  (i)  connected  to 
one  terminal  of  the  spark-gap,  the  opposite  terminal  being 
grounded  ;  a  generator  (A)  and  a  local  tuned  circuit  con- 

1  See  Figs.  74,  75,  and  76  in  Part  IV.,  p.  187. 


DESCRIPTIVE. 


77 


taining  a  capacity  (12)  in  parallel  with  the  sending  con- 
ductor for  the  purpose  of  prolonging  the  radiation. 


48       40  £ 


Fig.  29. 


Receiver.  —  At  the  receiving  end  is  employed  a  current- 
operated  wave-responsive-device1  in  a  closed  tuned  circuit 
(2,  3,  4,  5)  energized  by  the  receiving  conductor  (6)  con- 
taining the  primary  of  a  transformer. 

Circuit.  —  The  circuit  2,  3,  4,  5,  which  is  a  secondary 
circuit,  is  tuned  to  the  frequency  of  the  electromagnetic 
waves,  is  preferably  of  low  resistance,  and  has  a  larger 
ratio  of  inductance  to  capacity  than  that  of  the  receiving 
conductor.  This  is  for  the  purpose  of  protecting  the 
receiver  from  foreign  electrical  disturbances. 

Indicating  Mechanism.  —  "  Any  suitable  form  of  indicat- 
ing mechanism,  such  as  a  telephone  or  galvanometer,  may 
be  employed.  A  differentially-wound  indicating  mechan- 

1  See  Fig.  59,  p.  167,  Part  IV. 


78  WIRELESS   TELEGRAPHY. 

ism,  such  as  the  differentially-wound  telephone  41,  is  desir- 
able for  many  purposes,  and  has  one  circuit  connected 
across  the  receiver  14.  A  resistance  42,  preferably  formed 
by  a  loop  similar  to  the  receiver  14,  is  arranged  in  one  of 
the  circuits  of  the  differential  instrument,  the  receiver  14 
being  in  the  other  circuit,  so  that  the  circuits  are  balanced. 
Coils  43  and  44  are  oppositely  wound,  and  the  two  circuits 
being  balanced  there  is  normally  no  appreciable  effect  on 
the  diaphragm  45.  The  source  of  voltage,  46,  and  tuning- 
fork,  47,  are  used  to  produce  intermittent  currents  in  the 
differential  circuits,  and,  as  mentioned  above,  there  is  nor- 
mally no  effect.  When  an  electromagnetic  wave  causes  a 
current  to  pass  through  the  loop  14,  thereby  raising  its  re- 
sistance, the  current  in  circuits  containing  the  coils  44  of 
the  differential  instrument  is  weakened,  and  the  circuits 
being  out  of  balance  an  indication  is  produced  by  the 
instrument. 

Generation  may  be  Made  Continuous  Instead  of  Intermit- 
tent.—  "When  it  is  not  desired  to  use  an  intermittent  cur- 
rent,—  as,  for  example,  when  the  receiving  mechanism  is 
tuned  mechanically  to  a  given  note  for  selective  purposes, 
—  the  circuit  including  the  generator  is  made  continuous, 
as  by  wedging  the  prongs  of  the  tuning-fork,  or  in  any 
other  suitable  manner. 

Operation.  —  "  When  a  train  of  waves  is  radiated  from 
the  sending  station  and  received  by  the  receiving  conductor, 
it  causes  currents  to  flow  through  the  receiver,  I4,1  heat- 
ing it  up,  thereby  changing  its  resistance.  The  resistance 
of  the  differential  circuit  containing  the  receiver  is  there- 
fore increased,  the  current  therein  reduced,  and  sound  pro- 
duced by  the  telephone. 

1  See  Fig.  59,  p.  167,  Part  IV. 


DESCRIPTIVE.  79 

Transformer "  The  transformer  is  here   shown  as  a 

step-down  transformer,  as  this  form  has  advantages  when 
used  in  connection  with  current-operated  receivers  of  very 
low  resistance  ;  but  step-up  transformers  may  be  used." 

Means  of  Amplifying  Indications.  —  "  As  a  means  of 
amplifying  the  indications,  I  prefer  to  use  a  local  micro- 
phonic  circuit,  as  shown  in  Fig.  29,  where  a  small  carbon 
block,  36,  is  attached  to  the  diaphragm  of  the  differential 
telephone,  41,  and  a  carbon  point,  37,  bears  lightly  thereon. 
A  local  battery  generates  a  current  which  passes  continu- 
ously through  the  microphonic  contact  and  a  bridge  con- 
sisting of  the  arms,  39  39*  and  40  40%  and  a  siphon 
recorder,  48.  The  arms  of  the  bridge  are  balanced  as 
regards  ohmic  resistance.  Hence  for  all  steady  or  slowly 
varying  currents  no  portion  of  the  current  passes  through 
the  siphon  recorder.  The  arms  39  39*  have,  however,  very 
high  self-induction,  and  the  arms  40  40*  very  low  self-induc- 
tion, and  both  are  of  low  resistance.  On  any  sudden 
change  of  current,  such  as  will  be  produced  by  the  motion 
of  the  diaphragm  on  the  receipt  of  a  signal,  the  suddenly 
varying  current  cannot  flow  through  the  arms  39  39%  but 
will  flow  through  the  arms  40  40*  and  the  siphon  recorder, 
48,  thereby  producing  an  amplified  indication. 

Definitions  and  Uses  of  Closed  and  Open  Circuits.  —  "  The 

local  circuit  thus  formed  is  a  closed  circuit,  and  is  to  be 
differentiated  from  the  open  local  circuits  employed  in  con- 
nection with  the  coherer.  An  alternating-current  circuit 
may  be  closed  through  a  resistance,  an  inductance,  or  a 
capacity  ;  and  since  even  the  insulated  ends  of  a  circuit 


80  WIRELESS   TELEGRAPHY. 

will  always  have  some  capacity  relative  to  each  other,  it 
follows  that  all  alternating-current  circuits  are  theoretically 
closed.  What  is  meant,  therefore,  by  a  '  closed  alternating- 
current  circuit,'  is  a  circuit  in  which  the  current  is  rela- 
tively large  for  a  small  impressed  voltage  in  the  circuit,  — 
i.e.,  the  circuit  is  one  of  low  virtual  resistance  as  compared 
with  a  coherer.  By  an  '  unclosed '  or  '  open  '  circuit  is 
meant  one  in  which  the  current  is  relatively  small  or  neg- 
ligible for  a  small  impressed  voltage,  —  i.e.,  one  whose 
virtual  resistance  is  high.  Where  a  current-actuated  wave- 
responsive-device  is  employed,  a  closed  circuit  should  also 
be  employed  to  obtain  a  large  effective  current  to  actuate 
said-device.  Where  a  voltage-actuated  device,  such  as  a 
coherer,  is  employed  and  a  large  effective  difference  of 
potential  is  required,  an  open  circuit,  as  defined  above, 
should  be  used.  This  is  especially  important,  because 
while  a  resonant  rise  of  voltage  may  be  obtained  in  an  open 
circuit,  a  large  resonant  rise  of  current  is  possible  only  in 
a  closed  circuit  of  low  ohmic  resistance  used  in  connection 
with  a  source  of  maintained  radiation.  It  will  be  evident 
that  according  to  this  definition  of  closed  and  unclosed 
tuned  circuits,  in  many  cases  the  sending  or  receiving  con- 
ductor would  come  under  the  head  of  a  'closed  tuned 
circuit/  especially  when  having  large  capacity  and  low  in- 
ductance ;  but  where  reference  is  made  herein  to  a  '  closed 
tuned  circuit '  a  sending  or  receiving  conductor  is  not 
meant.  It  is  characteristic  of  these  closed  tuned  circuits 
that  they  have  a  peculiar  advantage  when  used  in  connec- 
tion with  the  form  of  receiver  in  that  such  circuits  act  to 
prevent  the  burning  out  of  the  receivers  by  electrical  dis- 
turbances produced  by  lightning  discharges.  They  also 
permit  of  the  employment  of  more  sensitive  current-actu- 


DESCRIPTIVE.  8l 

ated  wave-responsive-devices.  They  also  permit  of  step- 
down  transformers  being  used,  instead  of  step-up,  thus 
enabling  practically  all  of  the  energy  of  the  waves  to  be 
utilized,  and  giving  sufficient  inductance  with  small  length 
of  wire." 

Small  Voltages  Characteristic  of  Fessenden  Circuits.  — 
"  It  is  especially  characteristic  of  my  invention  —  i.e.,  the 
use  of  closed  tuned  circuits  in  connection  with  current- 
actuated  wave-responsive-devices  as  distinguished  from 
open  tuned  circuits  and  voltage-actuated  wave-responsive- 
devices  —  that  in  my  construction  the  voltages  in  the 
receiving  circuit  are  kept  small,  and  hence  practically  all 
the  energy  received  from  the  electromagnetic  waves  is 
employed  affecting  the  receiver,  and  hence  indications  can 
be  produced  by  an  amount  of  energy  which  is  an  extremely 
small  fraction  of  that  necessary  when  open  tuned  circuits 
and  voltage-actuated  wave-responsive-devices  are  employed. 

Practical  Test  of  Transmission.  —  "  Thus  since  the  ca- 
pacity of  a  coherer  is  small,  a  small  amount  of  energy  is 
sufficient  to  raise  it  by  itself  to  a  breakdown  voltage ;  but 
in  operation  it  is  connected  to  a  circuit  having  several 
hundred  times  the  capacity ;  and  as  this  circuit  must  be 
raised  to  practically  the  same  potential  as  the  coherer,  the 
efficiency  of  working  is  low  —  as,  for  example,  with  closed 
tuned  circuits  and  a  receiver,  messages  at  the  rate  of  thirty 
words  per  minute  were  sent  and  received  over  a  distance 
of  fifty  miles,  (i.e.,  from  Cape  Hatteras  to  Roanoke  Island,) 
using  a  spark  one  thirty-second  (^-)  of  an  inch  long  at  the 
sending  end.  When  a  coherer  and  an  open  tuned  circuit 
were  used  under  the  same  circumstances,  the  spark  length 


82  WIRELESS   TELEGRAPHY. 

had  to  be  increased  to  five  and  one-half  inches  before  any 
messages  could  be  received.  The  energies  in  the  two  cases 
were  approximately  in  the  ratio  of  one  to  forty  thousand. 

Definition  of  Current-Operated  Wave-Responsive-Device. 

—  "  By  the  term  <  current-operated  wave-responsive-de- 
vices '  as  used  herein  and  by  me  generally  is  meant  wave- 
responsive-devices  having  all  their  contacts  good  contacts, 
and  operated  by  currents  produced  by  electromagnetic 
waves.  They  are  hence  to  be  distinguished  from  wave- 
responsive-devices  depending  for  operation  upon  varying 
contact  resistance." 


DESCRIPTIVE.  83 


EHRET  S    DEVICE. 

30.  —  From  the  multitude  of  inventions  contribut- 
ing to  wireless  telegraphy  not  familiar  to  the  public,  one 
is  selected  here  as  representative  of  recent  advances  in 
this  art,  although  the  author  has  not  had  opportunity  from 
the  data  of  results  or  from  knowledge  of  experimental 
demonstrations,  to  judge  of  its  relative  importance.  The 
invention  is  described  in  United  States  Letters  Patent 
No.  699,158,  dated  May  6,  1902,  and  issued  to  Cornelius 
D.  Ehret  of  Washington,  D.C.  One  of  the  striking  feat- 
ures of  this  patent  is  its  comprehensive  brevity.  All  of 
the  drawings  are  shown  as  Fig.  30.  The  figure  I  extend- 
ing across  the  top  of  the  page  gives  a  detailed  representa- 
tion, and  the  other  six  drawings  illustrate  modifications  of 
the  first  organization.  While  the  space  is  well  filled,  it 
will  be  noted  that  there  is  neither  confusion  of  line  nor 
the  omission  of  any  necessary  detail.  The  description  of 
the  invention  is  equally  brief,  about  one  thousand  words 
sufficing  to  explain  seven  different  schemes  of  connections. 
• 

Recording  Mechanism.  —  In  the  figure  at  the  top  of  the 
page,  S  may  represent  a  register  which  records  dots  and 
dashes  in  ink  upon  paper  tape,  and  is  operated  whenever 
battery  B"  is  put  on  a  closed  circuit  by  reason  of  retractile 
spring  7  pulling  lever  4  against  contact  5.  When  the 
apparatus  is  at  rest,  lever  4  is  held  against  stop  6. 

Differential  Relay  (R).  —  It  will  be  noted  that  relay  R 
has  wound  differentially  about  its  core  3  two  coils/ and g\ 
and  consequently  if  electric  currents  of  the  same  strength 


WIRELESS    TELEGRAPHY. 


FIG.  I 


Fig.  30. 


DESCRIPTIVE.  85 

and  direction  be  sent   through   them   simultaneously  the 
effect  on  core  3  is  nil. 

Core  (3).  —  Core  3  in  itself,  without  the  aid  of  current 
effect,  is  slightly  magnetic ;  and  battery  B  and  coil  g  are 
so  arranged  that  their  influence  upon  core  3  is  to  induce  in 
it  a  magnetism  of  the  same  polarity  as  that  already  existing, 
and  so  to  increase  the  magnetic  effect. 

Coherer  (c) .  —  On  the  other  hand,  battery  B'  and  the 
winding  of  coil  f  are  arranged  to  work  in  opposition  to  coil  g 
and  battery  B.  c  is  the  usual  filings  coherer  which,  under 
the  influence  of  Hertzian  waves,  decreases  in  resistance. 
It  is  a  part  of  the  same  circuit  which  includes  battery  B' 
and  coil/. 

Anti-Coherer  (2).  —  2  is  a  device  called  an  anti-coherer, 
and  may  consist  of  tin-foil  glued  to  a  glass  plate,  as  in  a 
mirror,  and  with  slits  cut  across  the  metal  as  indicated  in 
the  drawing.  The  effect  of  etheric  impulses  upon  an 
anti-coherer  is  to  increase  its  resistance.  The  anti-coherer 
2  is  a  part  of  the  same  circuit  which  includes  battery  B 
and  coil  g}- 

Operation.  —  When,  therefore,  waves  from  a  distant 
source  impinge  upon  antenna  a  circuit  2  B  g  which  tends 
to  hold  lever  4  against  stop  6  is  greatly  weakened ;  and 
circuit  c  B'/ which  tends  to  repel  the  armature  of  lever  4 
is  made  much  stronger.  Consequently  the  magnetic  effect 
in  core  3  is  neutralized,  and  spring  7  draws  lever  4  against 
contact  5,  thus  actuating  S.  Tapping  the  coherer  c  during 

1  See  p.  154,  Part  IV.,   in  connection  with  "  anti-coherers." 


86  WIRELESS   TELEGRAPHY. 

the  absence  of  wave  effect  opens  circuit  c  B'y,  and  at  the 
same  instant  anti-coherer  2  regains  its  normal  conductivity 
and  the  armature  4  is  again  attracted  to  core  3. 

Advantages.  —  Presumably  the  advantages  attained  by 
this  plan  of  connection  are,  first,  greater  certainty  of  ac- 
tion ;  second,  a  closer  adjustment ;  third,  less  self -inductive 
influence  in  the  receiving  relay,  and  consequently  its 
quicker  action. 


DESCRIPTIVE.  87 


THE    DEFOREST    SYSTEM. 

Officials  connected  with  the  DeForest  system  claim  the 
best  record  for  accurate  service  during  the  naval  maneu- 
vers which  took  place  off  the  New  England  coast  in  the 
summer  of  1902.  The  principal  feature  of  their  system  is 
the  wave-responsive-device,  which  is  designated  by  its  in- 
ventors a  "responder."  This  instrument  is  described  as 
an  anti-coherer  in  Part  IV.,  and  is  illustrated  by  Fig.  49. 
In  connection  with  transmitters  the  DeForest  system  is 
further  described  in  the  same  division. 


WIRELESS    TRANSMISSION    OVERLAND. 

There  have  been  no  records  available  of  successful  ex- 
periments in  this  country  with  wireless  telegraphy  over- 
land, but  in  the  Marconi  article  in  the  Century  Magazine, 
March,  1902,  the  inventor  expressed  the  belief  that  the 
possibilities  for  inland  wireless  telegraphy  are  limited  to 
one  thousand  miles.  The  Federal  Wireless  Telephone 
Company  of  New  York  has  frequently  advertised  that  it 
was  about  to  open  communication  between  Baltimore  and 
Washington,  a  distance  of  forty  miles,  but  there  is  no 
record  of  a  test  for  even  so  far.  In  newspaper  interviews 
Mr.  Fessenden  is  reported  as  saying  that  his  apparatus  was 
about  to  be  tested  between  Annapolis  and  Washington, 
after  which  he  should  try  a  circuit  from  Chicago  to  New 
York  ;  but  directly  after  these  interviews  Lieutenant 
Beecher  of  the  United  States  Navy  declared,  in  a  paper 
before  the  American  Institute  of  Electrical  Engineers  on 
May  28,  that  he  believed  the  field  of  wireless  telegraphy  to 


88  WIRELESS   TELEGRAPHY. 

be  limited  to  the  ocean ;  and  Lieutenant  Beecher  is  sup- 
posed to  be  well  acquainted  with  the  Fessenden  apparatus. 
Overland  Contracts  in  Alaska.  —  The  chief  signal  officer 
of  the  United  States  Weather  Bureau  has  contracted  with 
the  Marconi  Company  for  a  circuit  of  one  hundred  and 
sixty-five  miles  in  an  air-line  from  Bates  Rapids  in  the  in- 
terior of  Alaska  to  Fort  Gibbon  near  the  sea-coast.  Ac- 
cording to  the  map  this  must  be  almost  entirely  overland, 
and  presenting  rather  difficult  conditions  at  that. 


NEW    MARCONI    RECEIVER. 

In  a  lecture  in  London  on  June  13,  1902,  Mr.  Marconi 
reported  that  he  had  invented  a  receiver  sufficiently  sensi- 
tive to  allow  of  a  transmission  at  the  rate  of  thirty  words 
per  minute.1 

GUARINl's    REPEATER. 

An  Italian  scientist,  Signer  Guarini,  seems  to  have 
been  partially  successful  in  designing  a  wireless-telegraph- 
repeater,  its  function  being  to  pick  up  signals  at  a  certain 
distance  and  relay  them  onward  with  renewed  strength. 


WIRELESS    TELEPHONY. 

Telephoning  without  wires  has  not  gained  by  the  great 
developments  in  its  sister-art.  Mr.  A.  F.  Collins,  an 
American,  reports  that  he  has  heard  faint  tones  at  a  dis- 
tance of  three  miles  through  what  he  terms  the  "  earth- 
bound-ether  ;  "  but  he  does  not  make  public  his  methods 

1  See  Fig.  58  and  accompanying  description  in  Part  IV.,  p.  165. 


DESCRIPTIVE.  89 

or  devices.  Telephonic  waves  are  readily  propagated 
through  space,  but  the  difficulty  is  to  confine  them  to 
an  intended  recipient.  Mr.  Collins  admits  that  the  prob- 
lem of  making  wireless  telephony  selective  is  one  calcu- 
lated to  discourage  the  most  sanguine  investigator.  The 
inventions  of  Professor  Pupin  have  decreased  the  first 
cost  of  telephone  equipment  and  increased  the  distance  of 
good  transmission.  Perhaps  a  multiplex  transmission  over 
one  small  copper  wire  connecting  the  two  points  will  even- 
tually be  the  best  device  for  selective  telephony. 

PRACTICABILITY. 

Notwithstanding  the  great  mass  of  positive  evidence, 
there  are  many  conservative  people  who  doubt  that  wire- 
less telegraphy  is  or  will  be  an  art  commercially  practica- 
ble. Public  exhibitions  have  so  often  proved  disappointing 
that  a  great  deal  of  disparaging  .testimony  has  circulated. 
Also,  there  has  lately  become  prominent  the  curious  fact 
that  sunlight  so  interferes  with  wireless  service,  that  to 
overcome  its  effect,  the  energy  necessary  for  transmission 
during  daylight  must  be  several  times  that  needed  for  the 
same  service  at  night ;  and  despite  previous  statements 
that  the  earth's  curvature  does  not  interfere  with  space 
signalling,  it  now  appears  that  for  equal  distances  there 
would  be  needed  over  a  flat  surface  only  one-third  of  the 
energy  now  required ;  but  these  facts  only  indicate  that 
more  power  must  be  applied  than  was  at  first  thought 
needful.  Always  the  public  is  looking  for  revolution  in 
an  art  and  almost  always,  after  the  original  discovery, 
progress  is  made  by  a  process  of  evolution  from  discoveries 
already  made.  It  may  with  comparative  safety  be  pre- 
dicted that  this  art,  as  have  most  others,  will  develop  with 


90  WIRELESS   TELEGRAPHY. 

step  by  step  movements  consisting  mainly  in  the  careful 
and  thorough  application  of  comparatively  small  yet  essen- 
tial details,  the  principles  of  which  are  already  well  under- 
stood, although  their  aggregate  importance  may  not  now 
be  fully  realized. 

To  illustrate  the  foregoing  by  analogies,  the  two  most 
essential  features  in  the  development  of  wire  telegraphy 
have  been  the  adoptions  of  screw-glass  insulators  and  of 
hard-drawn  copper  conductors ;  yet  copper  soft-drawn  was 
about  the  first  thing  tried  (being  soon  abandoned  for  iron), 
and  the  glass  insulator  at  first  without  the  screw  threads 
to  fasten  it  to  brackets  or  pins  has  been  in  use  from  the 
outset.  When  the  smooth-bore  glass  sprung  off  the  pin, 
as  it  often  did,  the  wire  lay  against  the  wood-work  and 
lost  part  of  its  current.  Again  hard-drawn  copper  was 
first  used  in  the  form  of  thin  wires,  and  although  it  has 
been  known  for  more  than  a  century  that  a  telegraph 
circuit  may  by  the  use  of  large  wires  be  operated  to 
proportionally  longer  distances  than  by  small  ones,  many 
years  elapsed  before  the  telegraph  companies  seemed  to 
realize  that  fact.  If  we  review  telephone  progress,  it  will 
be  found  that  one  of  its  important  steps,  the  transposition 
of  circuits  to  prevent  cross-talk,  was  fully  set  forth  twenty 
years  ago ;  *  but  that  it  was  ten  years  after  that  before 
such  transposition  was  systematized  and  made  effective. 

Professor  Fleming  of  the  Marconi  Company  has  recently 
reviewed  the  whole  art  of  wireless  telegraphy.  He  has 
positively  asserted  that  communications  may  be  carried 
on  between  stations  three  thousand  miles  apart,  and 
Professor  Fleming  has  had  every  opportunity  by  experi- 
ment and  observation  upon  which  to  base  such  an  assertion. 

*  In  U.  S.  Patent  to  author,  No.  240776,  filed  Sept.  28,  1880. 


MAXWELL 


BRANLY 


MARCONI 


H  E  RTZ 

LODGE 


PART  II. 


INVENTORS  AND    INVENTIONS. 

A  CURIOUS  feature  in  the  record  of  Wireless  Telegraphy 
is  the  fact  that  while  the  press  and  public  were  hailing  Mr. 
Marconi  as  the  only  inventor  of  all  that  pertained  to  the 
system  by  which  he  signaled  across  the  ocean,  the  name 
of  an  equally  important  patentee  was  hardly  mentioned. 

It  is  true  that  Professor  Silvanus  Thompson,  an  English 
electrician  of  repute,  had  once  or  twice  been  quoted  in 
newspaper  paragraphs  as  saying  that  the  Marconi  system 
was  a  direct  infringement  upon  American  patents  granted 
to  Professor  Lodge  ;  but  the  representatives  of  the  Mar- 
coni Company  disparaged  the  statement,  declaring  that 
Marconi  had  taken  out  eleven  United  States  patents  and 
Lodge  but  one. 

A  careful  search,  including  all  of  the  year  1902,  reveals 
only  ten  patents  issued  to  Marconi.  One  of  these,  how- 
ever, has  been  reissued,  and  may  have  been  counted  in 
addition.  On  the  other  hand,  at  the  date  of  the  transat- 
lantic transmission  by  Marconi  there  had  been  on  record 
for  several  months  the  award  of  very  important  claims  to 
Professor  Lodge  by  the  most  competent  tribunal  in  the 
world,  the  United  States  Patent  Office. 

It  is  not  purposed  to  make  this  writing  controversial, 
much  less  to  belittle  Marconi's  achievements.  That  in 

91 


92  WIRELESS   TELEGRAPHY. 

faith  in  himself  and  his  project,  in  force  of  character  and 
ability  to  inspire  confidence  in  others,  he  holds  very  high 
rank,  is  indisputable  ;  moreover,  he  must  be  recognized 
as  the  maker  of  an  epoch.  At  the  same  time,  the  historian 
of  this  art  would  be  remiss  who  did  not  endeavor  so  to  sift 
the  evidence  as  to  apportion  to  the  man  upon  the  pedestal 
only  his  due,  to  the  end  that  to  other  contributors  might 
come  rightful  credit. 

In  his  "  Evolution  of  the  Electric  Incandescent  Lamp," 
the  late  Franklin  Leonard  Pope  opens  the  preface  of  his 
first  edition  with  an  essay  upon  the  tendency  of  an 
unthinking  public  to  bestow  its  praise  for  a  new  invention 
upon  but  one  person.  Mr.  Pope,  in  1889,  when  this  was 
written,  was  a  recognized  authority  on  patent  matters,  as 
well  as  one  of  the  foremost  electrical  engineers.  He  said  : 

"  The  outcome  of  a  race  of  diligence  between  two  independent  but 
equally  meritorious  inventors  is  perhaps  as  often  as  otherwise  determined 
by  chance  or  accident.  In  this  respect  it  may  not  inaptly  be  compared  to 
the  result  of  a  horse-race  in  which  the  fortunate  winner  carries  off,  not  only 
all  the  honors,  but  the  purse  as  well,  although  his  nose  may  have  passed 
under  the  wire  barely  an  inch  in  advance  of  some  of  his  no  less  deserving 
competitors.  It  is  a  matter  of  common  observation  that  when  the  fullness 
of  time  arrives  the  discovery  or  invention  for  which  the  world  has  been 
waiting  is  certain  to  be  made.  The  critical  student  of  affairs  perceives  that 
however  wonderful  or  however  unexpected  that  invention  may  appear,  it 
is  seldom  that  it  is  not  found  to  be  a  necessary  sequence  of  a  long  series  of 
other  discoveries  and  inventions  which  have  preceded  it.  Even  in  those 
rare  cases  in  which  an  improvement  of  indisputable  novelty  and  originality 
is  made  known  to  the  industrial  world,  it  is  scarcely  ever  sufficiently  per- 
fected in  its  details  to  be  capable  of  practical  use  until  it  has  been  worked 
upon  and  improved  by  many  hands  and  many  minds. 

"  It  has  always  been  the  way  of  the  world  to  consider  every  such  inven- 
tion, especially  when  of  a  character  to  appeal  to  the  minds  of  the  masses, 
or  to  identify  itself  closely  with  the  everyday  life  of  the  community,  as  the 
work  of  some  particular  individual,  who,  as  it  were  by  common  consent,  is 
regarded  as  its  sole  originator  and  contriver,  and  upon  him  fame,  honor  and 


UNIVERSITY    i) 


OF 


IVENTORS   AND    INVENTIONS.  93 


wealth  are  lavished  without  stint,  in  childlike  unconsciousness  of  the 
universal  truth  that  inventions  of  this  character  are  not  made,  but  grow ; 
that  they  are  not  the  fruit  of  momentary  inspiration,  but  on  the  contrary  are 
the  inevitable  results  which,  from  time  to  time,  mark  the  slow  but  constant 
progress  of  scientific  and  industrial  evolution." 

Another  phase  of  popular  treatment  is  reaction,  which 
often  changes  from  adulation  to  indifference  or  positive 
condemnation.  Sinister  congratulations  from  the  Anglo- 
American  Cable  Company  were  the  immediate  fruits  of 
Marconi's  triumph  in  Newfoundland,  and  shortly  after- 
wards a  meeting  of  the  French  Academy  of  Science 
indulged  in  hostile  criticism.  The  speakers  at  that  meeting 
contended  that  documentary  evidence  showed  "that  credit 
for  the  invention  of  a  wireless  telegraph  is  due  first  to 
Feddersen  and  Maxwell  of  England,  then  to  Hertz  of 
Germany,  but  principally  to  Professor  Branly,  a  French- 
man, who  invented  the  coherer ;  then  to  Professor  Lodge 
of  England  and  Professor  Popoff  of  Russia.  Finally  it 
was  pointed  out  that  neither  the  French  army  nor  the 
German  navy  was  using  the  Marconi  system." 

Mr.  Pope,  in  his  "  Evolution  of  the  Electric  Incandes- 
cent Lamp,"  further  says:  "It  is  particularly  desirable 
that  the  line  of  demarcation  between  the  improvements 
which  unquestionably  involve  invention,  and  those  which 
really  exhibit  nothing  beyond  an  unusually  high  order  of 
mechanical  or  engineering  skill,  should  be  more  distinctly 
defined.  The  question  at  best  is  a  difficult  one ;  perhaps 
in  its  application  to  individual  cases  the  most  difficult  one 
which  the  courts,  sitting  in  patent  cases,  are  ever  called 
upon  to  determine."  ^ 

Probably  invention  will  be  always  more  or  less  intangible, 
and  thus  difficult  of  exact  definition.  Precedent,  however, 


94  WIRELESS   TELEGRAPHY. 

has  firmly  established  the  principle  that  inventive  genius 
must  be  something  more  than  the  manifestation  of  such 
technical  knowledge  and  skill  as  might  reasonably  be 
expected  of  a  person  trained  in  any  art.  The  inventor 
must  be  the  fortunate  one  who  has  moments  of  happy 
inspiration  leading  to  results  never  realized  by  hundreds 
of  faithful,  patient  plodders,  straining  to  reach  the  same 
goal.  Like  the  true  poet  or  artist,  the  inventor  is  born, 
not  made.  As  a  practical  test,  in  the  case  of  an  alleged 
invention,  the  question  might  be  raised  whether,  with  well- 
known  appliances  and  principles  and  furnished  with  the 
same  facilities  as  were  at  the  disposal  of  the  applicant  for 
a  monopoly,  a  hundred  skilled  mechanics  or  engineers 
could  have  achieved  the  same  result.  If  not,  and  if  the 
applicant  has  discovered  new  principles  or  devised  novel 
appliances,  then  he  has  made  a  true  invention.  Of  a 
number  of  necessary  qualifications  the  most  important  is 
that  originality  which  a  thorough  training  in  any  one  line 
tends  to  deaden. 

So  far  as  the  territory  of  the  United  States  is  con- 
cerned, the  claims  allowed  in  a  patent  are  to  some  extent 
a  warrant  of  monopoly  to  the  inventor.  The  burden  lies 
with  the  litigant  opposing  the  patentee  to  show  either  that 
the  Patent  Office  did  not  possess  all  the  information  bear- 
ing on  the  matter,  or  that  possessing  such  information  the 
Office  erred.  It  has  become  the  practice  of  examiners  to 
give  the  applicant  considerable  latitude  ;  and  as  at  that 
first  tribunal  there  is  no  opposing  counsel  to  break  down 
the  case,  it  often  happens  that  if  a  patent  is  subsequently 
contested  before  a  court  it  is  pronounced  invalid. 

In  the  report  of  the  Commissioner  of  Patents  for  1892 
appears  the  statement  that, 


INVENTORS   AND    INVENTIONS.  95 

"Of  988  court  cases  reported  in  the  Official  Gazette  of  the  Patent 
Office  between  1886  and  1892  wherein  patents  were  in  litigation,  436  pat- 
ents were  sustained  and  522  were  declared  invalid  in  whole  or  in  part.  Of 
the  number  declared  invalid,  428  were  by  reason  of  some  fault  in  the  Pat- 
ent Office,  and  124  on  account  of  evidence  brought  to  light  of  which  the 
Office  had  no  knowledge  before  granting  the  patents." 

Again  he  says  :  "Approaching  the  subject  from  another  side,  I  am  fur- 
nished with  the  result  of  examinations  as  to  the  validity  of  the  claims  in 
ten  patents  taken  at  random  where  searches  in  this  office  were  made  by  a 
well  known  law-firm.  These  patents  contain  fifty  claims,  of  which  thirty- 
five  were  considered  and  were  reported  to  be  old." 

Patent  Law  from  the  point  of  view  of  an  English 
scientist  is  discussed  by  Professor  Lodge,  in  his  "  Signal- 
ling Through  Space  Without  Wires,"  as  follows  : 

"  In  the  present  state  of  the  law  in  this  country  it  appears  to  be  neces- 
sary for  a  scientific  man  whose  investigations  may  have  any  practical  bear- 
ing, to  refrain  from  communicating  his  work  to  any  scientific  society,  or 
publishing  it  in  any  journal,  until  he  has  registered  it  and  paid  a  fee  to  the 
Government  under  the  so-called  Patent  LawT.  This  unfortunate  system  is 
well  calculated  to  prevent  scientific  men  in  general  from  giving  any  atten- 
tion to  practical  applications,  and  to  deter  them  from  any  attempt  to  make 
their  researches  useful  to  the  community.  If  a  scientific  worker  publishes 
in  the  natural  way,  no  one  has  any  right  in  the  thing  published.  It  is 
given  away,  and  lies  useless,  for  no  one  will  care  to  expend  capital  upon  a 
thing  over  which  he  has  no  effective  control.  In  this  case  practical  devel- 
opments generally  wait  until  some  outsider  steps  in  and  either  patents  some 
slight  addition  or  modification,  or  else,  as  sometimes  happens,  patents  the 
whole  thing  with  some  slight  addition. 

"  If  a  scientific  worker  refrains  from  publishing  and  himself  takes  out  a 
patent,  there  are  innumerable  troubles  and  possible  litigation  ahead  of  him, 
—  at  least  if  the  thing  turns  out  at  all  remunerative  ;  but  the  possibility  is^ 
that  in  his  otherwise  occupied  hands  it  will  not  so  turn  out  until  the  period 
of  his  patent  right  has  expired. 

"  Pending  a  much-to-be-desired  emendation  of  the  law,  whereby  the 
courts  can  take  cognizance  of  discoveries  or  fundamental  steps  in  an  in- 
vention communicated  to  and  officially  dated  by  a  responsible  scientific 
society,  and  can  thereafter  award  to  the  discoverer  such  due  and  moderate 
recompense  as  shall  seem  appropriate  when  a  great  indxistry  has  risen  on 
the  basis  of  that  same  discovery  or  fundamental  invention  ;  pending  this 


96  WIRELESS   TELEGRAPHY. 

much-to-be-desired  modification  of  the  law,  it  appears  to  be  necessary  to  go 
through  the  inappropriate  and  repulsive  form  of  registering  a  claim  to  an 
attempt  at  monopoly.  The  instinct  of  the  scientific  worker  is  to  publish 
everything,  to  hope  that  any  useful  aspect  of  it  may  be  as  quickly  as  possi- 
ble utilized,  and  to  trust  to  the  instinct  for  fair  play  that  he  shall  not  be  the 
loser  when  the  thing  becomes  commercially  profitable.  To  grant  him  a 
monopoly  is  to  grant  him  more  than  a  doubtful  boon ;  to  grant  him  the 
privilege  of  fighting  for  his  monopoly  is  to  grant  him  a  pernicious  privilege 
which  will  sap  his  energy,  waste  his  time,  and  destroy  his  power  of  future 
production." 

THE    CHAIN    OF    INVENTION. 

Reference  to  Professor  Dolbear's  patent  printed  in  the 
appendix  reveals  a  well  denned  transmission  of  electric 
waves  without  wires  in  1882;  and  the  historical  part  of 
this  work  records  instances  of  wireless  signaling  nearly 
half  a  century  before  that  date.  (See  Achievement.) 

Upon  May  23rd,  1885,  Mr.  Thomas  A.  Edison  filed 
an  application  for  a  United  States  Patent,  which  was 
finally  issued  upon  December  2Qth,  1891,  numbered 
465,971.  It  differs  from  Dolbear's  organization  in  that  a 
key  is  used  to  send  out  signals  instead  of  a  telephone  to 
transmit  words.  The  receiving  apparatus  may  be  a  tele- 
phone or  other  recording  apparatus.  The  Edison  speci- 
fication sets  forth  all  the  uses  to  which  a  wireless  telegraph 
may  be  put,  such  as  transmitting  signals  from  a  shore  to 
moving  vessels,  signalling  across  bodies  of  water  in  lieu 
of  using  submarine  cables  ;  and  as  well  across  land  spaces. 
It  provides  for  the  earth's  curvature  by  interposing  along  a 
route  condensing  surfaces  so  arranged  that  there  shall  be 
always  a  clear  air  space  between  any  surface  and  its  im- 
mediate neighboring  ones  in  either  direction. 

It  is  reported  that  this  patent  has  been  purchased  by 
the  Marconi  interests.  It  has  five  years  to  run.  The 
first  claim  is  as  follows  : 


INVENTORS   AND    INVENTIONS.  97 

"CLAIM  i.  Means  for  signalling  between  stations  separated  from  each 
other,  consisting  of  an  elevated  condensing  surface,  or  body  at  each  station, 
a  transmitter  operatively  connected  to  one  of  said  condensing  surfaces  for 
varying  its  electrical  tension  in  conformity  to  the  signal  to  be  transmitted 
and  thereby  correspondingly  varying  the  tension  of  the  other  condensing 
surface ;  and  a  signal  receiver  operatively  connected  to  said  other  conden- 
sing surface  substantially  as  described. 

CLAIM  2  adds  to  the  combination  a  condensing  surface  at  such  eleva- 
tion that  a  straight  line  between  said  surfaces  and  the  terminal  surfaces 
will  avoid  the  curvature  of  the  earth's  surface.  Claim  3  adds  an  induction 
transmitter.  Claim  4  brings  in  the  secondary  and  the  primary  of  an  induc- 
tion coil,  a  transmitting  key,  and  a  telephone  receiver.  Claim  5  has  a  new 
combination  of  the  elements  previously  noted." 

All  of  these  earlier  transmissions,  however,  are  supposed 
to  have  been  due  to  the  propagation  through  space  of 
magnetic  lines  of  force,  or  magnetic  waves.  The  period 
of  ethereal  transmission  dates  from  the  discoveries  in  1886 
of  Professor  Hertz,  of  Carlsruhe,  Germany,  who  found 
that  a  disruptive  discharge  of  electricity  across  a  spark- 
gap  produced  a  wave  motion  essentially  different  from  the 
magnetic  movement.  His  receiver  of  these  waves  was  a 
piece  of  wire  so  bent  as  to  bring  its  ends  almost  together. 
(Fig.  48.)  In  the  little  space  between  the  ends  of  the 
bent  wire  he  detected  a  response  to  the  discharges  from  a 
Ruhmkorff  coil.  These  responses  were  in  the  form  of 
minute  sparks.  Between  the  spark-gap  of  the  machine  and 
the  bent  wire  there  was  no  tangible  conductor  of  any  kind. 
The  adjective  "  Hertzian  "  in  the  patents  of  Lodge  and  of 
Marconi  are  acknowledgements  to  the  physicistofCarlsruhe. 

Contemporaneously  with  the  work  of  Hertz,  Professor 
Calzecchi-Onesti,  an  Italian  scientist,  devised  apparatus 
consisting  of  a  glass  tube  containing  metal  filings,  and 
revoluble  on  an  axis.  He  found  that  a  group  of  filings 
which,  under  normal  conditions,  gave  a  very  great  resist- 
ance to  an  electric  current,  became  a  good  conductor  if 


98 


WIRELESS   TELEGRAPHY. 


subjected  to  the  secondary  impulse  that  occurs  when  an 
electric  wire  circuit  is  broken ;  but  if,  after  the  discharge 
had  ceased,  the  glass  tube  containing  the  filings  was 
turned  over  in  such  a  way  as  to  disarrange  them,  the 
filings  became  again  a  highly  resistant  mass. 

Branly's  Discovery,  1891.  —  In  1891  Professor  Branly 
of  the  Catholic  Institute  of  Paris,  made  the  discovery  that 
electric  sparks  across  an  air-gap  caused  filings  to  cohere, 


VERTICAL  WIRE 


TREMBLER 

MAGNET 


EARTH 


and  also  that  a  shock  or  tap  imparted  to  the  tube  served  to 
decohere  them.  The  coherer  has  since  been  commonly 
called  the  "  Branly  tube."  It  would  seem,  however,  that 
in  the  matter  of  a  tube  of  filings,  Professor  Onesti  is  more 
properly  entitled  to  the  honor  of  being  the  originator. 

Popoff's  Early  Devices.  —  In  April,    1895,  Professor.  A. 
Popoff,    of    the  Cronstadt  Torpedo  School,  described    to 


INVENTORS   AND    INVENTIONS.  99 

the  Russian  Physico-Chemical  Society  of  St.  Petersburg 
a  device  which  he  was  using  in  connection  with  the  study 
of  atmospheric  electricity,  and  in  December  of  the  same 
year  he  said  in  a  note  to  that  Society  that  he  hoped  to 
make  his  apparatus  applicable  to  telegraphic  signaling. 

Description  of  Fig.  31.  —  There  is  shown  in  Fig.  31  the 
organization  used  by  Popoff.  The  line  in  the  diagram 
marked  "  vertical  wire "  was  his  exploring  antenna  for 
atmospheric  electrical  manifestations.  It  may  be  explained 
that  the  parts  represented  as  separated  at  the  point  X  are 
in  contact  when  the  apparatus  is  at  rest.  When  waves 
from  a  distant  point  impinge  upon  the  vertical  wire  they 
pass  through  the  coherer  to  earth,  changing  the  coherer 
from  an  insulating  path  to  a  conducting  one.  This  change 
causes  a  current  to  flow  from  battery  B  through  the  relay. 
The  relay  magnet,  thus  becoming  energized,  pulls  down 
armature  A  which  has  been  held  upward  by  spring  S, 
making  contact  at  Z.  There  results  a  division  of  current 
at  Y  and  Y',  by  which  the  trembler  magnet  is  caused  to 
pull  upward  the  armature  A'  and  sound  an  alarm  on  the 
call-bell.  This  upward  movement  of  A'  destroys  the 
contact  at  X,  and  spring  S'  draws  down  A',  the  mo- 
mentum imparted  to  knob  K  serving  to  make  it  tap  the 
coherer. 

Dr.  Lodge  as  a  Patentee.  — From  the  allowed  claims  of 
his  United  States  patents,  Dr.  Lodge  would  seem  to  con- 
stitute the  most  important  link  in  the  chain  of  inventors  of 
wireless  telegraphy.  An  inspection  of  his  claims  shows 
that  he  is  recognized  as  the  originator  of  the  "  emitter," 
the  single  conducting  body  from  which  waves  are  sent  into 


100  WIRELESS    TELEGRAPHY. 

space ;  of  the  metal  shield  which  protects  the  receiving 
apparatus  from  damage  or  from  operation  by  the  trans- 
mitter at  the  same  station  with  it ;  of  the  automatic  means 
of  decohering  the  trembler  in  a  local  circuit ;  of  the  com- 
bination with  a  coherer  and  battery  of  a  telegraphic 
receiving  instrument ;  and  finally  of  the  scheme  of  syn- 
tonizing which  attunes  by  adjustments  of  inductance  and 
capacity. 

Professor  Lodge's  system  has  already  been  explained. 
The  ofBcial  recognition  of  his  inventions  is  recorded  in  his 
United  States  patents  numbered  674,846,  the  application 
for  which  was  filed  December  20,  1897,  and  609,154,  for 
which  the  application  was  filed  in  1898.  A  reproduction 
of  the  first  is  printed  in  full  in  the  appendix  of  this  work. 
The  data  and  claims  of  the  second  are  as  follows  : 

No.  609,154,  Oliver  f.  Lodge,  Liverpool,  England,  Dated  August  j6,  1898. 
Application  filed  February  i,  i8g8. 

CLAIM  i.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination, 
with  a  pair  of  capacity  areas,  of  a  self-inductance  coil  inserted  between  them 
electrically  for  the  purpose  of  prolonging  any  electrical  oscillations  excited 
in  the  system,  and  constituting  such  a  system  a  radiator  of  definite  fre- 
quency or  pitch. 

CLAIM  2.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination, 
with  a  pair  of  capacity  areas,  of  a  self-inductance  coil  inserted  between  them 
electrically  for  the  purpose  of  prolonging  any  electrical  oscillations  excited 
in  the  system,  thus  constituting  the  system  a  resonator  or  absorber  of  defi- 
nite frequency  or  pitch,  and  a  distant  radiator  of  corresponding  period 
capable  of  acting  cumulatively. 

CLAIM  3.  In  a  system  of  Hertzian- wave  telegraphy,  the  combination, 
with  a  pair  of  capacity  areas,  of  electrical  means  having  a  spark-gap  inserted 
between  them  and  serving  to  syntonize  them,  and  means  for  bridging  or 
shunting  the  spark-gap,  whereby  the  apparatus  is  adaptable  for  use  at  will 
either  as  a  radiator  or  resonator. 

CLAIM  4.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination^ 
with  a  pair  of  capacity  areas,  of  a  number  of  self -inductance  coils  having 


INVENTORS   AND    INVENTIONS.  IOI 

different  amounts  of  self-induction,  each  of  which  is  capable  of  being 
switched  in  or  out  of  circuit,  serving  to  syntonize  any  such  radiator  to  a 
corresponding  resonator  or  vice  versa,  whereby  signaling  may  be  effected 
between  any  two  or  more  correspondingly-attuned  stations  without  disturb- 
ing other  differently-attuned  stations. 

CLAIM  5.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination, 
with  a  pair  of  capacity  areas,  of  a  variably-acting  self -inductance  coil,  serv- 
ing to  syntonize  such  a  radiator  or  resonator  to  any  other  such  resonator 
or  radiator,  whereby  signaling  may  be  effected  between  any  two  or  more 
correspondingly-attuned  stations  without  disturbing  other  differently-attuned 
stations. 

CLAIM  6.  In  combination,  a  pair  of  capacity  areas  connected  by  a  coil 
of  wire  serving  as  the  radiator  in  a  system  of  Hertzian-wave  telegraphy, 
means  for  syntonizing  such  radiator,  and  means  for  charging  it  by  aerial 
disruption  or  impulsive  rush. 

CLAIM  7.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination  of 
a  pair  of  capacity  areas  such  as  h,  h',  means  for  syntonizing  such  capacity 
areas,  a  receiving-circuit  completed  through  one  or  both  of  such  capacity 
areas,  and  means  for  bridging  over  the  discharge-gap  between  such  capacity 
areas  when  they  are  to  be  used  as  a  receiver,  whereby  such  capacity  areas 
are  rendered  adaptable  for  use  at  will  either  as  a  radiator  or  resonator. 

CLAIM  8.  In  combination,  in  a  system  of  syntonic  Hertzian-wave  tele- 
graphy, a  pair  of  capacity  areas,  a  self-inductance  coil  and  a  secondary  coil 
surrounding  said  self-inductance  coil,  which  secondary  coil  forms  part  of  the 
coherer-circuit  substantially  as  and  for  the  purpose  set  forth. 

CLAIM  9.  The  combination,  in  the  receiving-circuit  of  a  system  of  Hertz- 
ian-wave telegraphy,  of  a  variably-acting  self-inductance  coil,  connecting 
the  capacity  areas,  a  coherer,  a  battery,  a  receiving  instrument,  and  a  shunt 
across  the  coils  thereof  substantially  as  and  for  the  purpose  set  forth. 

Declaration  in  Marconi's  U.  S.  Patent.  —  Regarding 
priority  in  invention,  a  quotation  from  the  specification  of 
the  reissue  of  Marconi's  first  American  patent  is  herewith 
given.  It  may  be  explained  that  statements  of  this  char- 
acter embodied  in  a  patent  do  not  constitute  official  recog- 
nition, such  recognition  being  confined  to  the  allowed 
claims.1 

1  See  pp.  102,  103,  and  200. 


102  WIRELESS   TELEGRAPHY. 

"  I  am  aware  of  the  publication  of  Professor  Lodge  of  1894  at  London, 
England,  entitled  'The  Work  of  Hertz,'  and  the  description  therein  of 
various  instruments  in  connection  with  manifestations  of  Hertz  oscillations. 
I  am  also  aware  of  the  papers  by  Professor  Popoff  in  the  '  Proceedings  of 
the  Physical  and  Chemical  Society  of  Russia 'in  1895  or  1896',  but  in 
neither  of  these  is  there  described  a  complete  system  or  mechanism  capable 
of  artificially  producing  Hertz  oscillations,  and  forming  the  same  into  and 
propagating  them  as  definite  signals,  and  reproducing,  telegraphically,  such 
definite  signals;  nor  has  any  system  been  described,  to  my  knowledge,  in 
which  a  Hertz  oscillator  at  a  transmitting-station,  and  an  imperfect-contact 
instrument  at  a  receiving-station,  are  both  arranged  writh  one  terminal  to 
earth  and  the  other  elevated  or  insulated  ;  nor  am  I  aware  that  prior  to  my 
invention  any  practical  form  of  self-recovering  imperfect-contact  instrument 
has  been  described.  I  believe  that  I  am  the  first  to  discover  and  use  any 
practical  means  for  effective  telegraph  transmission  and  intelligible  reception 
of  signals  produced  by  artificially  formed  Hertz  oscillations." 

INITIAL    AMERICAN    PATENT    OF    GUGLIELMO    MARCONI. 

For  United  States  Patent  No.  586,193,  the  application 
by  Marconi  was  filed  December  7,  1896.  The  patent  was 
issued  July  13,  1897,  with  fifty-six  claims,  and  remained  as 
the  record  until  June  4,  1901,  when  it  was  reissued  as 
No.  11,913,  in  which  the  fifty-six  claims  were  replaced  by 
twenty-four.  The  complete  reissued  record  is  reproduced 
in  the  appendix  of  this  work. 

MARCONI'S  UNITED  STATES  PATENTS. 

Initial  American  Patent.  —  Considering  now  the  re- 
issued claims  of  the  initial  American  patent  of  Marconi, 
the  first  one  is  a  combination  of  the  three  elements,  —  an 
imperfect  contact,  a  current  through  it,  and  a  receiving 
instrument  operated  by  the  influence  of  distant  oscilla- 
tions on  the  contact.  The  second  claim  is  also  a  combina- 
tion of  three  elements,  —  an  imperfect  contact,  a  current 


INVENTORS   AND    INVENTIONS.  103 

through  it,  and  means  operated  by  the  circuit  to  shake  the 
imperfect  contact. 

CLAIM  3.  The  third  claim,  while  it  combines  as  many  as 
seven  elements,  appears  to  be  an  essential  one.  It  reads  : 

A  spark-producer, 

An  earth-connection  to  one  end  of  the  spark-producer, 

An  insulated  conductor  to  the  other  end, 

An  imperfect  contact, 

An  earth-connection  to  one  end  of  the  contact, 

An  insulated  contact  to  the  other  end, 

A  circuit  through  the  contact. 

The  important  features  of  this  combination,  the  use  of 
ground  connections  with  the  transmitter  and  the  receiver, 
is  suggested  by  Dolbear's  patent.  (See  Appendix.) 

Metal  Shield  Around  Receiver.1  --  Marconi's  second 
patent,  by  filing  of  application,  is  No.  624,5 1 6.  It  has  three 
claims  of  length,  each  bringing  forward  as  one  element  a 
metallic  box  inclosing  the  receiver.  The  object  of  this  is 
to  prevent  injury  to  the  receiver,  on  account  of  its  close 
proximity  to  the  sparking  appliance  when  both  sender  and 
receiver  are  used  at  one  station.  Metal  screens  to  protect 
the  receiver  from  a  near-by  transmitter  are  disclosed  in 
Marconi's  initial  American  patent  filed  in  1896.  The 
same  principle  is  also  the  subject  of  Professor  Lodge's 
third  claim  in  No.  674,846,  filed  a  year  earlier  than  Mar- 
coni's 624,516,  and  is  fully  described  in  Lodge's  specifica- 
tion. Consequently  a  broad  claim  was  not  possible  at  the 
date  of  filing  of  the  metal  shield  application. 

Marconi* s  Third  American  Patent.  —  Marconi,  on  Janu- 
ary 5,  1899,  filed  an  application  for  a  U.  S.  patent  which 

1  See  Figs.  6g  and  70  in  Part  IV,,  with  accompanying  descriptions. 


104  WIRELESS   TELEGRAPHY. 

was  issued  June  27,  1899,  as  No.  627,650.  Its  first  claim 
is  here  broken  into  paragraphs  to  distinguish  the  different 
elements. 

CLAIM  i.     In  a  receiver  for  electrical  oscillations,  the  combination  of 
An  imperfect  contact  (the  coherer}, 
A  local  circuit  through  it, 
An  induction  coil, 

A  capacity  (either  a  condenser  or  the  earth], 
A  conductor  connected  to  one  end  of  the  primary  of  the  coil  (the  high 

wire), 
A  connection  between  the  other  end  and  the  capacity  (i.e.,  the  primary 

to  earth], 
Connections  between  the  ends  of  the  imperfect  contact  and  the  ends 

of  the  secondary  coil, 
A  condenser  in  one  of  the  latter  connections.1 

There  are  eight  claims,  all  of  them  in  connection  with 
a  receiver  for  electrical  oscillations.  Claim  2  adds  to  the 
combination  in  No.  i  as  protection  to  the  coherer,  choking 
coils,  which  also  appear  in  the  initial  Marconi  American 
patent.  Claims  3,  4,  5,  and  6  introduce  an  induction  coil 
in  which  the  primary  and  secondary  windings  are  each  of 
but  a  single  layer ;  and  claims  7  and  8  modify  these  layers 
in  that  they  are  composed  of  wires  not  exceeding  one- 
fiftieth  centimeter  in  diameter  (T^  inch).  Regarding 
single-layer  windings,  Marconi  himself  in  future  patents 
made  continued  modification. 


MARCONI'S  FOURTH,  FIFTH,  AND  SIXTH  AMERICAN  PATENTS. 

On  June  13,  1899,  Marconi  filed  an  application  which 
was  afterwards  divided  and  finally  issued  in  the  form 
of  three  U.  S.  patents,  numbered  respectively  647,007, 

1  Italicized  words  in  parentheses  supplied  by  the  author  as  explanatory. 


INVENTORS   AND    INVENTIONS. 


105 


647,008,  and  647,009.  In  these  specifications  is  much  mat- 
ter in  common,  the  forty  claims  for  the  three  patents  being 
made  thus  voluminous  to  cover  technical  points.  Two 
drawings  have  been  selected,  —  Fig.  32,  the  main  illustra- 
tion of  both  the  first  and  third  of  the  series,  and  Fig.  33, 


Fig.  32- 


the  principal  drawing  in  the  second  of  the  series.  The 
quotation  here  presented  is  common  to  all  three  of  the 
series  : 


"  This  invention  relates  to  improvements  in  the  apparatus  described  in 
the  specification  of  Patent  No.  627,650,  granted  to  me  June  27,  1899.     In 


io6 


WIRELESS   TELEGRAPHY. 


that  specification  I  described  connecting  the  aerial  conductor  to  a  capacity 
which  may  be  the  earth  through  the  primary  of  an  induction-coil,  the  ends 
of  the  imperfect  contact  or  sensitive  tube  being  connected  to  the  ends  of  the 
secondary.  In  place  of  winding  both  the  primary  and  secondary  in  single 
layers,  as  claimed  in  that  specification,  the  coils  are  now  either  made  very 
short  (not  much  exceeding  two  centimeters  in  length)  or  else  are  wound  in 
sections.  The  number  of  turns  in  the  successive  layers  of  the  secondary 


Fig.  33- 

(and  sometimes  of  the  primary  also)  should  diminish  as  the  distance  from 
the  center  increases ;  but  this,  although  preferable,  is  not  essential.  It  is 
also  found  desirable  to  connect  direct  to  the  sensitive  tube  or  imperfect 
contact  (not  through  the  condenser)  the  end  of  the  secondary  which  is 
farthest  away  from  the  nucleus  or  axial  line  of  the  coil. 

"  In  description  of  Figs.  32  and  33,  a  is  the  aerial  conductor;   l>,  a  local 
battery ;  c,  a  condenser ;  e,  a  connection  to  earth  or  other  suitable  capacity  •„ 


INVENTORS   AND    INVENTIONS.  107 

/,  a  sensitive  tube  or  imperfect  contact ;  k  are  choking-coils,  and  r  a  relay 
working  a  signaling  or  other  instrument.  The  diagrams  of  the  coils  are 
greatly  enlarged  half-longitudinal  sections,  but  are  not  strictly  to  scale. 
In  place  also  of  showing  the  section  of  each  coil  or  layer  of  wire  as  a  longi- 
tudinal row  of  dots  or  small  circles,  as  it  would  actually  appear,  it  is  for 
simplicity  shown  as  a  single  continuous  longitudinal  straight  line.  A  is  the 
end  of  the  primary,  wrhich  is  connected  to  the  aerial  conductor  #,  and  E  is 
the  end  connected  to  earth  or  a  capacity.  J  is  the  end  of  the  secondary, 
which  is  directly  connected  to  the  sensitive  tube  or  imperfect  contact/,  and 
C  is  the  end  which  is  connected  to  it  through  the  condenser.  G  is  a  glass 
tube  on  which  the  coils  are  wound.  The  wires  are  preferably  insulated  by 
a  single  covering  of  silk." 

Claims  I,  2,  and  16  fairly  illustrate  the  inventive  scope 
of  the  first  one  of  this  group,  No.  647,007,  and  are  as 
follows  : 

CLAIM  i.  In  a  receiver  for  electrical  oscillations,  the  combination  of 
an  imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil, 
the  secondary  of  which  consists  of  several  layers,  the  number  of  turns  in 
the  outer  layers  being  less  than  in  those  next  the  primary,  a  capacity 
connected  to  one  end  of  the  primary,  a  conductor  connected  to  the  other 
end,  and  connections  between  the  ends  of  the  imperfect  contact  and  the 
ends  of  the  secondary. 

CLAIM  2.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil,  the 
secondary  of  which  consists  of  several  layers,  the  number  of  turns  in  the 
outer  layers  being  less  than  in  those  next  the  primary,  a  capacity  connected 
to  one  end  of  the  primary,  a  conductor  connected  to  the  other  end,  con- 
nections between  the  ends  of  the  imperfect  contact  and  the  ends  of  the 
secondary,  and  a  condenser  in  one  of  the  latter  connections, 

CLAIM  16.  In  a  receiver  for  electrical  oscillations,  the  combination  of 
an  imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil, 
the  primary  of  which  consists  of  two  wires  connected  in  parallel,  wound  in 
four  layers,  the  first  and  second  layers  being  formed  of  one  wire  and  the 
third  and  fourth  of  the  other,  the  secondary  of  which  consists  of  several 
layers,  the  number  of  turns  in  the  outer  layers  being  less  than  in  those  next 
the  primary,  and  wound  unsymmetrically  with  a  lump  at  one  end,  a  capacity 
connected  to  one  end  of  the  primary,  a  conductor  connected  to  the  other 


I08  WIRELESS   TELEGRAPHY. 

end,  connections  between  the  ends  of  the  imperfect  contact  and  the  ends 
of  the  secondary,  and  a  condenser  in  one  of  the  latter  connections. 

Claims  /,  2,  and  4  of  the  second  of  tJie  group  are  inserted 
to  show  the  distinctive  features  of  that  patent.  Words  are 
Italicized  by  the  author  to  mark  a  phrase  which  does  not 
occur  in  the  first  patent,  but  is  found  in  all  three  of  the 
following  claims : 

CLAIM  i.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil,  the 
secondary  of  which  consists  of  several  layers,  the  number  of  turns  in  the 
outer  layers  being  less  than  in  those  next  the  primary,  a  capacity  connected 
to  one  end  of  the  primary,  a  conductor  connected  to  the  other  end,  connec- 
tions between  the  ends  of  the  imperfect  contact  and  the  ends  of  the  sec- 
ondary, and  a  condenser  in  the  connection  to  the  inner  end  of  the  secondary, 

CLAIM  2.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil,  the 
secondary  of  which  consists  of  several  layers,  the  number  of  turns  in  the 
outer  layers  being  less  than  in  those  next  the  primary,  and  wound  unsym- 
metrically  with  a  lump  at  one  end,  a  capacity  connected  to  one  end  of  the 
primary,  a  conductor  connected  to  the  other  end,  connections  between  the 
ends  of  the  imperfect  contact  and  the  ends  of  the  secondary,  and  a  con- 
denser in  the  connection  to  the  inner  end  of  the  secondary. 

CLAIM  4.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil,  the 
primary  of  which  consists  of  two  wires  connected  in  parallel,  wound  in  two 
layers,  the  secondary  of  which  consists  of  several  layers,  the  number  of 
turns  in  the  outer  layers  being  less  than  in  those  next  the  primary,  and 
wound  unsymmetrically  with  a  lump  at  one  end,  a  capacity  connected  to 
one  end  of  the  primary,  a  conductor  connected  to  the  other  end,  connec- 
tions between  the  ends  of  the  imperfect  contact  and  the  ends  of  the  sec- 
ondary, and  a  condenser  in  the  connection  to  the  inner  end  of  the  secondary. 

Of  the  last  of  the  series  but  one  claim,  the  sixteenth,  is 
shown  where  the  Italicized  word  "  two  "  is  its  only  distinc- 
tion from  claim  16  of  the  first  of  the  series,  in  which  the 
word  "  four  "  is  also  found  in  Italics. 


INVENTORS   AND    INVENTIONS.  IOQ 

CLAIM  16.  In  a  receiver  for  electrical  oscillations,  the  combination  of 
an  imperfect  electrical  contact,  a  local  circuit  through  it,  an  induction-coil, 
the  primary  of  which  consists  of  two  wires  connected  in  parallel,  wound  in 
two  layers,  the  secondary  of  which  consists  of  several  layers,  the  number  of 
turns  in  the  outer  layers  being  less  than  in  those  next  the  primary,  and 
wound  unsymmetrically  with  a  lump  at  one  end,  a  capacity  connected  to 
one  end  of  the  primary,  a  conductor  connected  to  the  other  end,  connec- 
tions between  the  ends  of  the  imperfect  contact  and  the  ends  of  the  sec- 
ondary, and  a  condenser  in  one  of  the  latter  connections. 


INVENTION    OF     IMPROVED     TRANSMITTING     KEYS,    SEVENTH 
AND    EIGHTH    AMERICAN    PATENTS    OF    MARCONI. 

Patent  No.  650,110,  filed  December  28,  1899,  *s  a  modi- 
fication of  No.  650,109,  filed  on  October  12  of  the  same 
year.  The  diagram  which  illustrates  the  former  is  shown 
as  Fig.  77  in  connection  with  "  Keys,"  Part  IV.  The 
difference  between  the  two  patents  is  that  in  the  first  a 
connection  is  made  from  that  electrode  of  the  spark-gap 
which  connects  with  the  high  wire  to  an  insulated  back 
terminal  on  the  sending-key  of  the  transmitting  operator ; 
while  in  the  second  patent  the  high  wire  connecting 
directly  with  the  insulated  back  terminal  of  the  transmit- 
ting key  does  not  make  actual  contact  with  the  electrode 
of  the  spark-gap,  but,  instead,  is  brought  very  near  to  it. 

The  first  claim  of  650,109  is  as  follows  : 

CLAIM  i.  The  combination  of  the  primary  and  secondary  of  a  sparking 
appliance,  a  battery  and  key  in  circuit  writh  the  primary,  an  aerial  conductor 
connected  to  one  terminal  of  the  secondary,  a  receiver,  means  for  connect- 
ing the  said  terminal  to  the  receiver,  and  a  capacity  connected  to  the  other 
terminal. 

In  the  second  claim  there  are  substituted  for  the  last 
eight  words  of  Claim  i  the  words  "  and  an  earth  connec- 
tion connected  to  the  other  terminal." 

The  first  claim  of  No.  650,110  is  as  follows: 


I  IO 


WIRELESS   TELEGRAPHY. 


CLAIM  i.  The  combination  of  the  primary  and  secondary  of  a  spark- 
ing appliance,  a  battery  and  key  in  circuit  with  the  primary,  an  aerial  con- 
ductor led  in  close  proximity  to  one  terminal  of  the  secondary,  means  for 
connecting  the  said  aerial  conductor  to  the  receiving  instrument,  and  a 
capacity  connected  to  the  other  terminal. 

The  change  of  phrase  noted  in  the  companion  patent, 
whereby  "  capacity  "  is  substituted  for  "earth  connection,'' 
occurs  here  also. 


NINTH    AMERICAN    PATENT    OF    MARCONI. 

In  Fig.  34  there  is  shown  a  new  set  of  connections  in 
which  the  secondary  winding  of  a  step-down  induction  coil 
is  divided  into  two  parts,  a  condenser 
is  placed  between  the  two  parts,  and 
the  relay  circuit  is  connected  to  them 
on  each  side  of  that  condenser.  This 
diagram  is  the  principal  drawing  of 
U.  S.  Patent  No.  668,315,  issued  on 
February  19,  1901,  the  application  for 
which,  however,  was  filed  July  17,  1900. 
While  it  is  not  the  broadest  claim, 
No.  4  offers  the  best  brief  to  illustrate 
the  invention.  It  is  given  here  with 
interpolated  explanatory  references  as  follows  : 

CLAIM  4.  In  a  receiver  for  electrical  oscillations,  the  combination  of 
an  induction  coil,  the  secondary  of  which  is  wound  in  two  parts  (see  /2, 
Fig.  34),  an  aerial  conductor  connected  to  one  end  of  the  primary  (A),  a 
capacity  connected  to  the  other  end  of  the  primary  (E),  a  detector  or 
coherer  connected  to  the  outer  ends  of  the  secondary  (T),  a  condenser 
across  the  inner  ends  of  the  secondary  (73),  a  local  circuit  connected  to  the 
condenser  (BR),  choking  coils  between  the  local  circuit  and  condenser 

(ClC2). 


INVENTORS   AND    INVENTIONS. 


I II 


No.  i,  the  broadest  claim,  has  but  five  elements,  and 
reads  as  follows  : 

CLAIM  i.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
induction-coil,  the  secondary  of  which  is  wound  in  two  parts,  an  aerial  con- 
ductor connected  to  one  end  of  the  primary,  a  capacity  connected  to  the 
other  end  of  the  primary,  a  detector  connected  to  the  outer  ends  of  the 
secondary,  and  a  local  circuit  connected  to  the  inner  ends  of  the  secondary. 

The  wording  of  one  part  of  the  specification  leads  to  the 
belief  that  at  the  date  of  its  filing,  July  17,  1900,  the  in- 
ventor was  beginning  to  question  the  efficacy  of  the 


Fig.  35- 


Fig.  36. 


tmsymmetrical  winding  advocated  in  former  patents,  al- 
though he  still  gives  to  it,  as  Fig.  35,  precedence  in  order 
of  description.  The  arrangement  shown  in  Fig.  36,  how- 
ever, is  spoken  of  as  one  from  which  "  very  good  results  have 
been  obtained."  In  it  each  half  of  the  secondary  consists 
of  one  hundred  and  sixty  turns  in  a  single  layer.  The 
specification  states  that  in  using  coils  in  which  the  second- 
ary winding  consists  of  one  layer,  the  inventor  had  noticed 
that  the  best  results  were  had  when  the  length  of  the 
secondary  winding  was  approximately  equal  to  the  length 
of  the  aerial  conductor  employed  at  the  transmitting 
station,  an  observation  somewhat  in  line  with  Professor 
Slaby's  assertion  that  there  is  a  law  of  transmission 
which  governs  the  length  both  of  the  emitter  and  the 
antenna.1 

1  See  in  connection  with  Slaby,  p.  58. 


112 


WIRELESS   TELEGRAPHY. 


DOUBLE    WAVE-GATES.       TENTH    AMERICAN    PATENT    OF 
MARCONI. 

At  this  writing  the  final  Marconi  patent,  so  far  as 
known,  is  No.  676,332.  The  application  was  filed  Febru- 
ary 23,  1901,  and  it  was  issued  on  June  11  of  the  same 
year.  It  relates  to  the  employment  of  double  emitters 


. 

— -~<5flffl^|-0  ©^-1 
t     e     \ 

LvWW\AV-J 


Fig.  37- 

and  antennae.  These  double  conductors  are  shown  either 
as  concentric  cylinders  separated  by  an  appreciable  air- 
space, or  as  two  distinct  vertical  wires,  or  as  an  aerial 
terminal  consisting  of  two  conductors  arranged  concentri- 
cally, the  inner  one  being  a  solid  wire  covered  with  an 
insulating  substance,  and  the  outer  being  a  tube  fitting 
closely  around  the  insulation  of  that  which  forms  the  core. 


INVENTORS   AND    INVENTIONS.  113 

The  typical  diagram  is  Fig.  37,  in  which  it  may  be  noted 
that  the  inner  conductor  has  one  branch  to  earth  and  one 
through  an  inductance  and  the  spark-gap  to  the  outer  one. 
In  other  drawings  the  patentee  shows  at  the  transmitting 
station  the  wire  connecting  secondary  coil  c  with  induct- 
ance i  to  the  left  as  having  a  pointed  top,  and  resting 
against  one  of  the  coils  of  z,  thus  indicating  that  the 
inductance  may  be  varied.  The  scope  of  this  final  Mar- 
coni patent  may  be  shown  by  an  analysis  of  its  five  claims 
as  follows : 

CLAIM  i.  Element  one,  —  Two  aerial  oscillation-producing  conductors 
insulated  from  each  other.  Element  two,  —  An  inductance  connected  in 
series  with  such  conductors.  Element  three,  —  A  producer  of  electric 
oscillations  (a  Ruhmkorff  coil,  for  instance).  Element  four,  —  A  signaling 
instrument  controlling  the  spark-producer  (as  a  key  in  the  primary 
circuit).1 

CLAIM  2.  There  is  added  to  the  combination  in  claim  i  a  fifth  element, 
a  connection  from  one  of  the  emitters  to  the  earth. 

CLAIM  3.  Element  one  of  first  claim  is  modified  by  the  statement  that 
the  two  aerial  oscillation-producing  conductors  are  insulated  from  each 
other. 

CLAIM  4.  Pertains  to  a  receiving  station  and  has  four  elements:  One. 
Two  antennae  insulated  from  each  other.  Two.  An  inductance  con- 
nected in  series  with  the  two  antennae.  Three.  An  imperfect  electrical 
contact. 

CLAIM  5.  Adds  to  the  combination  in  claim  4  a  connection  from  one 
of  the  antennae  to  the  earth. 

There  occurs  in  the  specification  of  the  patent  now 
under  consideration  the  remark  that  while  "  Lodge  shows 
two  large  oscillation-producing  conductors  and  an  induct- 
ance device  connected  between  them,"  yet  he  does  not 
"use  a  plurality  of  aerial  oscillation-producing  conduc- 
tors."2 

1  Parenthetical  phrases  supplied  by  author. 

2  See  claims  6  and  8,  Lodge's  patent,  No.  609,154,  p.  101,  Part  II. 


114  WIRELESS   TELEGRAPHY. 


THE    WIRELESS    TRANSMISSION    PATENTS    OF    TESLA. 

A  number  of  inventions  by  Mr.  Nikola  Tesla  have  been 
described  at  length  in  Part  I.  Their  relation  to  the  general 
patent  situation  is,  however,  so  complex,  and  may  prove  so 
far  reaching  that  anything  like  an  exhaustive  discussion  of 
such  of  his  numerous  patents  as  bear  upon  the  art,  would 
occupy  many  times  the  space  which  can  be  allotted  in  this 
work.  Anything  less  than  an  exhaustive  discussion  would 
not  do  the  subject  justice.  It  has,  therefore,  been  thought 
best  to  reproduce  in  the  appendix,  without  any  comment 
whatever,  the  numbers,  titles,  dates  of  filing  and  represen- 
tative claims,  of  such  patents  as  may  seem  to  give  to  the 
inventor  a  monopoly  of  any  of  the  methods  and  devices 
necessary  to  the  proper  working  of  a  wireless  telegraph 
system. 

UNITED    STATES    PATENTS    OF    PROFESSOR    REGINALD 
A.     FESSENDEN. 

On  August  12,  1902,  there  were  issued  to  Professor 
Fessenden  thirteen  United  States  patents,  which  are  here 
considered  in  the  order  of  their  filing  as  applications. 

Fessenden' s  Initial  United  States  Patents.  —  The  first 
two,  filed  December  15,  1899,  and  numbered  706,735  and 
706,736,  are  companion  patents,  one  concerning  the  meth- 
ods and  the  other  the  devices  of  the  same  improvements. 

The  first  claim  of  the  method  patent  reads : 

CLAIM  I.  "As  an  improvement  in  the  art  of  transmitting  signals  elec- 
trically by  electromagnetic  waves,  the  method  herein  described,  which  con- 


INVENTORS   AND    INVENTIONS.  115 

sists  in  the  generation  of  electromagnetic  waves  at  one  station  and  trans- 
forming the  energy  of  the  currents  generated  by  such  waves  at  the  receiv- 
ing-station into  the  energy  of  motion,  that  is  without  the  necessary  interpo- 
sition of  a  secondary  or  auxiliary  generator  for  the  production  of  such 
motion." 

The  auxiliary  generator  referred  to  as  omitted  is  pre- 
sumably the  battery  which  in  coherer  organizations  actu- 
ates the  relay.  It  will  be  observed  that,  as  represented  in 
Fig.  55,  Part  IV.,  there  is  no  source  of  energy  whatever 
at  the  receiving  station. 

To  a  feature  of  this  invention  attention  is  called  by 
another  claim,  as  follows : 

CLAIM  6.  "  As  an  improvement  in  the  art  of  transmitting  electrical  en- 
ergy by  electromagnetic  waves,  the  method  herein  described,  which  consists 
in  prolonging  the  oscillations  of  an  energy-radiating  conductor  by  energy 
from  a  source  external  to  the  radiating-conductor  and  tuned  to  the  period 
of  the  radiating-conductor." 

The  external  source  here  is  condenser  18  in  a  shunt  cir- 
cuit around  the  spark-gap  as  shown  in  Fig.  44,  Part  IV. 

Another  novel  feature  is  set  forth  in  the  ninth  claim, 
and  explained  by  Fig.  53,  Part  IV.,  and  the  accompanying 
description. 

CLAIM  9.  "As  an  improvement  in  the  art  of  transmitting  electrical 
energy,  the  method  herein  described,  which  consists  in  varying  the  con- 
ductivity of  a  secondary  circuit  at  the  receiving-station  by  motion  produced 
by  currents  generated  by  electromagnetic  waves." 

The  Device  Patent The  device   patent    707,636  has 

the  same  drawings  as  706,735.  Its  claims  cover  in  gen- 
eral the  means  and  combination  of  means  which  are  used 
in  the  methods  specified  and  claimed  in  its  mate. 


n6 


WIRELESS   TELEGRAPHY. 


Fessenden's  Patent  for  Electro-Magnetic  Sending  Con- 
ductor.—  No.  706,737  was  filed  May  29,  1901.  Here 
No.  17  is  a  characteristic  claim  for  a  sending  conductor. 

CLAIM  17.  "A  sending-conductor  for  electromagnetic  waves  having  low 
resistance,  small  self-induction  and  great  capacity." 

An  illustration  of  the  above  is  found  in  reference  num- 
ber i  of  Fig.  38. 

Another  feature  is  the  receiver  of  claim  12,  which  is 
shown  in  Fig.  55,  Part  IV.  The  claim  entire  reads, — 


Fig. 


CLAIM  12.  "A  system  for  signaling  by  electromagnetic  waves,  having 
in  combination  a  conductor' adapted  to  ladiate  waves  of  low  frequency,  and 
a  receiver  dependent  for  its  action  upon  a  constant  or  independently-vary- 
ing magnetic  field  and  adapted  to  respond  to  currents  produced  by  said 
waves." 


Fig.  38,  as  a  whole,  illustrates  a  system  covered  fairly 
well  by  claim  21,  which  reads  : 

CLAIM  21.  "A  system  for  transmission  of  energy  by  electromagnetic 
waves,  including  in  combination  a  radiating-conductor  and  a  source  of  alter. 
nating  electrical  energy  or  potential,  said  radiating-conductor  and  source 
being  co-ordinated  and  relatively  adjusted  to  radiate  a  substantially  con- 
tinuous stream  of  electromagnetic  waves  of  substantially  uniform  strength." 


INVENTORS   AND    INVENTIONS.  117 

Fessenden's  U.  S.  Patent  for  Localizing  by  the  Use  of  a 

Plurality  of  Tuned  Circuits The  features  of  No.   706,- 

738,  filed  May  29,  1901,  are  well  indicated  by  its  claims  I 
and  5  here  quoted,  and  as  an  illustrating  diagram  refer- 
ence is  had  to  Fig.  26,  Part  I. 

CLAIM  i.  "In  a  system  of  signaling  by  electromagnetic  waves,  a  receiv- 
ing-conductor having  a  transforming  device  in  series  in  the  circuit,  in  com- 
bination with  a  circuit  including  a  translating  device,  and  having  a  local 
source  of  voltage  and  controlled  by  the  transforming  device  and  a  source  of 
voltage  so  arranged  that  its  voltage  will  oppose  the  voltage  from  the  local 
source  operating  the  translating  device. 

CLAIM  5.  In  a  system  of  signaling  by  electromagnetic  waves,  a  send- 
ing-conductor  adapted  to  maintain  and  to  radiate  persistent  oscillations,  in 
combination  with  a  receiving-conductor  and  one  or  more  secondary  circuits 
controlled  by  the  receiving-conductor,  the  ratio  of  inductance  to  capacity 
being  larger  in  a  secondary  circuit  than  in  the  sending-conductor,  a  wave- 
responsive  device  included  in  a  secondary  circuit  of  a  series,  the  several  cir- 
cuits being  each  tuned  to  correspond  to  the  period  of  the  sending-conductor." 

Fessenden's  United  States  Patent  for  Increasing  the 
Capacity  of  the  Wave-Gate.  —  The  Fessenden  patent 
706,739  covers  a  device  for  surrounding  the  wave-gate 
with  a  medium  of  specific  inductive  capacity  higher  than 
air.  Figs.  62  and  63  in  Part  IV.  are  respectively  a  plan 
and  an  elevation,  and  are  there  fully  described.  The  first 
of  the  twenty  claims  may  be  quoted  as  follows  : 

CLAIM  i,  "A  conductor  for  radiating  electromagnetic  waves,  in  combi- 
nation with  a  medium  having  an  electrical  constant  on  which  the  wave 
length  depends  of  a  value  greater  than  that  of  air  arranged  in  suitable 
relation  to  the  conductor." 

Fessenden's  United  States  Patent  for  Localization  by 
Generating  and  Receiving  Two  Sets  of  Waves  of  Different 

Periodicities No.  706,740,  filed  September  28,  1901,  is 

an  ingenious  device  for  the  localization  of  signals.     It  is 


Il8  WIRELESS    TELEGRAPHY. 

described  at  length  in  connection  with  Fig.  28,  Part  I.     Of 
the  nine  claims  two  are  sufficient  for  illustration.1 

CLAIM  i.  "In  a  system  of  signaling  by  electromagnetic  waves,  the 
combination  of  a  source  of  waves  of  different  periodicities  and  two  or 
more  receivers  responsive  respectively  to  the  differing  waves  or  impulses 
and  a  wave-responsive  device  operative  when  the  waves  or  impulses  attain 
a  certain  predetermined  phase  relation. 

CLAIM  6.  In  a  system  of  signaling  by  electromagnetic  waves,  the  com- 
bination of  means  at  the  sending-station  for  generating  two  or  more  sets 
of  waves  of  different  periodicities,  and  a  wave-responsive  device  at  the 
receiving-station  operative  by  the  conjoint  action  of  such  set  of  waves." 

Fessenden's  Wireless  Telephony. — The  interesting  claim 
of  Patent  No.  706,747,  filed  September  27,  1901,  is  the 
fourteenth  referring  to  Wireless  Telephony  as  follows  : 

CLAIM  14.  "  In  a  system  for  transmission  of  speech  by  electromagnetic 
waves,  the  combination  at  the  sending-station  of  means  for  the  practically 
continuous  generation  of  electromagnetic  waves,  a  telephone-transmitter 
for  modifying  the  character  of  the  waves  or  impulses,  and  a  telephone- 
receiver  at  the  receiving-station  responsive  to  currents  generated  by  the 
electromagnetic  waves." 

An  illustration  of  the  above  is  Fig.  27  in  Part  I.,  and 
there  described. 

Fessenden's  High  Pressure  Spark-Gap.  —  Professor  Fes- 
senden's  Patent  706,741,  filed  November  5,  1901,  is  for  a 
device  to  maintain  a  certain  definite  relation  between  the 
resistance  and  the  self-inductance  and  capacity  of  the  send- 
ing mechanism,  regardless  of  the  potential  employed.  It  is 
described  at  length  in  connection  with  Figs.  46  and  47, 
Part  IV.  To  indicate  its  patentable  scope,  two  of  its  claims 
are  subjoined. 

CLAIM  5.  "An  apparatus  for  the  generation  of  radiation,  having  in 
combination  a  conductor  for  radiating  electromagnetic  waves,  and  sparking 

1  See  in  Part  I.  description  of  Tesla  Patents,  Nos.  723,188  and  725,605,  and  in  Appendix 
their  dates  and  claims. 


INVENTORS   AND    INVENTIONS.  119 

*    '     - 

terminals,  all  gaps  between  sparking  terminals  being  occupied  by  insulating 
material  under  pressure  greater  than  atmospheric  pressure,  substantially  as 
set  forth. 

CLAIM  n.  An  apparatus  for  the  generation  of  radiation  having  in 
combination  a  conductor  for  radiating  electromagnetic  waves  and  spark- 
ing terminals,  all  gaps  between  sparking  terminals  being  occupied  by 
insulating  material  under  pressure  above  a  certain  critical  high  pressure." 


Fessenden's  Patent  for  a  Selective  System.  —  In  con- 
nection with  "Keys"  in  Part  IV.,  will  be  found  as  Figs. 
74,  75,  and  76,  a  reproduction  of  the  third  sheet  of  draw- 
ings of  the  Fessenden  Patent  No.  706,742,  filed  June  6, 
1902. 

This  document  is  long,  containing  five  sheets  of  draw- 
ings, six  printed  pages  of  specifications,  and  twenty-nine 
claims. 

To  show  its  features,  five  of  the  claims  follow : 


CLAIM  5.  "  In  a  system  for  signaling,  &c.,  by  electromagnetic  waves, 
the  combination  of  a  conductor  adapted  to  radiate  electromagnetic  waves, 
means  for  causing  the  radiation  of  electromagnetic  waves  from  said  con- 
ductor, and  means  for  modifying  one  or  more  of  the  characteristics  of  said 
waves. 

CLAIM  9.  In  a  system  of  signaling  by  electromagnetic  waves,  the  com- 
bination of  a  conductor  and  a  spark-gap  with  means  for  changing  the 
function  of  the  conductor,  i.e.,  from  sending  to  receiving  without  bridging 
or  disconnecting  the  spark-gap. 

CLAIM  16.  In  a  system  of  signaling  by  electromagnetic  waves,  the 
combination  of  a  receiving-circuit,  a  series  of  receivers,  and  means  shifting 
any  desired  one  of  said  receivers  into  and  out  of  operative  relation  to  the 
receiving-conductor. 

CLAIM  21.  A  system  of  signaling  by  electromagnetic  waves,  having  in 
combination  a  sending-conductor  and  a  key  provided  with  fingers  adapted 
to  be  brought  into  contact  in  succession  with  the  sending-conductor  at 
different  points. 

CLAIM  26.    A  system  of  signaling  by  electromagnetic  waves,  having  in 


120  WIRELESS    TELEGRAPHY. 

combination  therewith  means  for  indicating  to  a  third  station  during  send- 
ing or  receiving  that  such  sending  or  receiving  station  is  busy." 

Fessenden's  Patent  for  Recording  on  Photographic  Paper. 

—  Patent  No.  706,743,  filed  June  26,  1902,  is  for  a  method 
of  catching  the  signals  on  photographic  paper,  and  at  the 
same  time  and  in  the  same  procedure  applying  chemicals 
to  fix  and  develop  them.  There  are  but  three  claims,  which 
are  herewith  reprinted. 

CLAIM  i.  "As  an  improvement  in  the  art  of  signaling  by  electro- 
magnetic waves,  the  method  herein  described,  which  consists  in  producing 
interpretable  characters  or  symbols  on  a  strip  or  film  by  chemical  action 
produced  by  currents  generated  by  electromagnetic  waves. 

CLAIM  2.  As  an  improvement  in  the  art  of  signaling  by  electro- 
magnetic waves,  the  method  herein  described,  which  consists  in  affecting  a 
sensitive  strip  or  film  by  currents  generated  by  electromagnetic  waves. 

CLAIM  3.  As  an  improvement  in  the  art  of  signaling  by  electromag- 
netic waves,  the  method  herein  described,  which  consists  in  producing 
interpretable  characters  or  symbols  on  a  strip  or  film  by  chemical  action 
induced  by  electric  currents  generated  by  electromagnetic  waves." 

Fessenden's      Electromagnetic-Receiving-Device.  —  No. 

706,744,  filed  July  i,  1902,  is  for  an  electromagnetic 
receiving-device.  It  is  described  at  length  in  connection 
with  Fig.  59,  Part  IV.  The  first  three  claims  are  suffi- 
ciently characteristic  to  show  its  patentable  scope. 

CLAIM  i.  "  A  receiver  for  currents  produced  by  electromagnetic  waves 
consisting  of  a  conductor  having  small  heat  capacity. 

CLAIM  2.  A  receiver  for  currents  produced  by  electromagnetic  waves 
consisting  of  a  conductor  having  small  radiating-surface. 

CLAIM  3.  A  receiver  for  currents  produced  by  electromagnetic  waves 
consisting  of  a  conductor  having  low  resistance  and  small  heat  capacity 
substantially  as  set  forth." 

Fessenden's  Patent  for  System. — There  will  be  found 
in  connection  with  Fig.  29,  Part  I.,  a  long  description  of 


INVENTORS   AND    INVENTIONS.  121 

the  invention  embodied  in  No.  706,745,  filed  July  I,  1902. 
The  patent  is  for  a  system,  and  presumably  presents  the 
culmination  of  Mr.  Fessenden's  labors.  Of  its  thirty 
claims  the  twenty-ninth  may  be  quoted. 

CLAIM  29.  "A  system  ot  signaling  by  electromagnetic  waves,  having  at 
the  receiving-station  a  closed  tuned  secondary  circuit  and  a  constantly-re- 
ceptive, current-operated,  wave-responsive  device,  in  combination  with  a 
source  of  persistent  radiation  at  the  sending-station." 

Fessenden's  Wave-Chute  Patent Professor  Fessenden's 

patent,  No.  706,746,  filed  July  i,  1902,  is  for  a  wave-chute. 
It  is  fully  described  in  connection  with  wave-gates,  and 
illustrated  by  Figs.  64  and  65,  Part  IV.  One  claim  is  as 
follows. 

CLAIM  5.  "  In  a  system  for  the  transmission  of  energy  by  electromag- 
netic waves,  a  sending-conductor  for  radiating  such  waves,  and  an  artificial 
ground  connected  to  the  lower  end  of  the  sending-conductor  and  connected 
at  its  outer  end  to  ground." 


NOTICEABLE    GROUP    OF    INVENTORS. 

It  is  impossible  within  the  limits  of  this  volume  to  men- 
tion, even  briefly,  all  the  inventions  in  this  young  art,  for 
they  are  already  numbered  by  hundreds.  There  is  a  notice- 
able group  of  inventors  who  assign,  either  directly  or 
indirectly,  to  the  American  Wireless  Telegraph  Company. 
Among  them  Mr.  A.  F.  Collins  and  Mr.  Harry  Shoe- 
maker are  prominent,  the  latter  being  especially  prolific. 
Unfortunately  there  is  no  public  record  of  quantitative 
results  by  which  the  merits  of  their  inventions  may  be 
measured. 


122  WIRELESS   TELEGRAPHY. 


EHRET  S    COMBINATION    OF    COHERER    AND    ANTI-COHERER. 

The  patent  of  Mr.  Cornelius  D.  Ehret,  already  noticed 
at  some  length  as  of  promise,1  is  deserving  of  consideration 
from  an  inventive  standpoint.  It  is  numbered  699,158. 
The  application  was  filed  December  3,  1901,  and  the  issue 
is  dated  May  6,  1902.  It  contains  twelve  claims,  all  of 
value.  Three  of  them  are  herewith  reprinted. 

CLAIM  i.  "In  a  signaling  system  the  combination  of  dissimilar  wave- 
responsive  devices  conjointly  controlling  a  translating  device. 

CLAIM  7.  In  a  receiver  the  combination  of  a  coherer  and  an  anti- 
coherer  conjointly  controlling  a  translating  device. 

CLAIM  12.  In  a  receiver  the  combination  of  a  coherer  and  an  anti- 
coherer,  a  local  circuit  controlled  by  each,  a  coil  of  a  relay  included  in  each 
circuit,  said  coils  operating  differentially  on  the  magnetic  circuit  of  each 
relay,  substantially  as  described." 


PUPIN     PATENTS. 

Dr.  M.  I.  Pupin,  of  Columbia  University,  has  taken  out 
two  United  States  patents  for  multiple  telegraphy  with 
conductors.  His  claims,  however,  may  have  so  broad  a 
scope  as  to  cover  the  principle  of  selective  signalling  by 
means  of  electrical  resonance  ;  and  for  this  reason  it  is 
reported  that  his  rights  have  been  purchased  by  the  Mar- 
coni interests.  The  numbers  are  respectively  707,007,  and 
707,008,  and  both  were  i'ssued  on  August  I2th,  1902. 
Application  for  the  first  was  filed  February  23rd,  1894. 
As  an  illustration  of  their  bearing  upon  wireless  telegraphy, 
claim  number  one  of  the  earlier  patent  (707,007)  is  here- 
with quoted  : 

1  See  p.  84  and  Fig.  30  in  Part  I. 


INVENTORS    AND    INVENTIONS.  123 

"CLAIM  i.  The  method  of  distributing  electrical  energy  which  consists 
in  throwing  upon  a  common  conductor  a  number  of  alternate  currents  of 
different  frequencies  and  distributing  the  several  energies  of  these  currents 
each  selectively  to  a  separate  electrical  device  substantially  as  described." 

SUMMARY. 

There  is  in  Part  I  an  account  of  the  transmission  of 
electric  signals  by  Morse  in  1 842  across  a  body  of  water ; 
and  a  similar  achievement  by  Lindsay  some  ten  years  later. 
In  the  next  decade  James  Clark  Maxwell  published  his 
interpretation  of  electrical  phenomena  as  a  propagation  of 
ether  waves,  differing  from  light  only  in  the  lesser  number 
of  vibrations  within  a  given  unit  of  time.  In  1882  Dol- 
bear  applied  for  a  United  States  Patent  for  a  method  of 
telephonic  transmission  across  space  without  wires ;  and  in 
1885  Edison  applied  for  one  to  cover  methods  and  devices 
similar  to  Dolbear's.  It  seems,  however,  that  the  true 
period  of  invention  in  the  field  of  ethereal  transmission 
extends  from  the  discovery  of  the  minute  sparks  in  the 
bent  wire  at  Carlsruhe  in  1886,  to  the  reception  of  the 
Poldhu  signals  at  Cape  Race  in  1901  ;  that  the  first  trans- 
mission was  due  to  Hertz,  and  the  discovery  of  the  .prop- 
erties of  the  filings  to  Calzecchi-Onesti ;  that  the  researches 
of  Branly  gave  to  the  world  the  laws  which  govern  the 
action  of  the  coherer ;  that  Lodge  sealed  the  filings  in  a 
vacuum,  applied  to  the  coherer  thus  improved  the  prin- 
ciples of  electrical  resonance,  and  in  a  laboratory  combined 
the  various  elements  which  make  a  wireless  telegraph ; 
that  Tesla  discovered  many  of  the  laws  governing  high  fre- 
quencies and  great  pressures  and  devised  means  for  the 
production  and  effective  insulation  of  high  potentials;  and 
finally  Marconi  combined  the  results  of  these  various  dis- 
coverers in  a  system  by  which  signals  were  observed  at  the 
distance  of  two  thousand  miles. 


124 


WIRELESS   TELEGRAPHY. 


THE    COMPARATIVE    MERITS.  125 


PART 


THE   COMPARATIVE   MERITS 

OF  WIRELESS  TELEGRAPHY  AND  OF  TELEGRAPHY 
BY  WIRES  AND  CABLES  — AND  THE  COM- 
MERCIAL OUTLOOK  FOR  EACH. 

THE  history  of  the  useful  arts  is  evidence  of  the  fact 
that  each  new  development  adapts  itself  to  an  especial 
field ;  that  old  methods  and  devices,  which  seemed  certain 
to  be  supplanted  by  new,  often  continue  to  be  employed 
and  even  to  multiply.  The  innumerable  freight  trains  that 
now  rumble  between  Buffalo  and  Albany  have  not  dis- 
placed the  mule  and  barge  of  Erie  Canal ;  and  notwith- 
standing the  existence  of  unnumbered  freight-carrying  iron 
steamers,  wooden  vessels  with  sail  power  are  still  being 
built  on  the  Kennebec.  Millions  of  electric  lamps  illumine 
the  streets,  theatres,  hotels,  and  residences  of  New  York 
City,  yet  "dollar  gas"  was  very  recently  an  issue  in  its 
politics.  The  pedestrians  of  our  larger  cities  are  compelled 
at  each  street  crossing  to  calculate  the  relative  speed  of 
machine-moved  vehicles  ;  yet  the  last  United  States  Census 
records  twenty-two  millions  of  horses  and  mules  ;  and  all 
the  harness  factories  in  the  country  at  this  writing  are 
behind  their  orders.  Telephone  instruments  are  installed 
in  every  nook  and  corner  of  the  City  of  New  York,  their 


126  WIRELESS   TELEGRAPHY. 

daily  connections  counting  into  thousands  ;  yet  the  mes- 
senger business  of  the  American  District  Telegraph  has 
not  decreased  during  the  last  seventeen  years,  and  that 
company  is  still  paying  dividends. 

It  is  the  purpose  of  this  section  to  speculate  as  to  the 
influence  that  will  be  exerted  by  Wireless  Telegraphy  upcn 
its  predecessors  and  competitors  in  the  field  of  distant 
communication.  The  new  art  has,  of  course,  an  exclusive 
and  profitable  employment  in  signaling  from  ship  to  ship 
on  the  ocean,  and  from  ship  to  shore.  The  English 
Marconi  Company  already  derives  a  revenue  from  tolls  for 
communications  between  passengers  on  incoming  steam- 
ships and  the  near  shores,  receiving  about  two  hundred  and 
fifty  dollars  a  voyage  from  messages  sent  within  a  short 
distance  of  either  side  of  the  Atlantic.  The  Lloyds  have 
adopted  the  system,  and  are  requiring  steamships  that  get 
the  best  insurance  rates  to  be  equipped  with  it.  It  is  easy 
to  prophesy  that  in  the  immediate  future  the  telegraphic 
news  of  the  world  will  be  scattered  like  seed  from  the  sower 
over  the  whole  Atlantic  and  may  be  picked  up  by  any  vessel 
equipped  with  properly  attuned  apparatus ;  but  that  it  will 
render  the  present  system  of  ocean  cables  obsolete  is  alto- 
gether improbable. 

Ocean  Cables  as  a   Means  of    Communication.  —  The 

cables  are  an  excellent  medium  for  the  transmission  of 
signals  ;  they  are  in  position  ;  and  the  money  that  has 
been  expended  to  make  and  to  place  them  cannot  now 
be  recovered.  Neither  bonded  indebtedness,  nor  other 
form  of  financial  obligation,  will  have  any  physical  effect 
upon  the  efficiency  of  the  cables  as  a  means  of  communi- 
cation. 


THE    COMPARATIVE    MERITS.  127 

Expression  of  the  Cable  Company's  Official.  —  In  this 
connection  may  be  quoted  an  article  from  the  New  York 
Sun  of  March  4th,  1902,  entitled  "The  Cable  Company 
Cheerful  "  : 

An  expression  of  confidence  in  the  ability  of  submarine  cables  to  main- 
tain their  commercial  supremacy  in  competition  with  wireless  telegraphy 
was  made  yesterday  by  George  G.  Ward,  Vice- President  and  General  Man- 
ager of  the  Commercial  Cable  Company,  in  addressing  as  chairman  the 
annual  meeting  of  that  company's  shareholders  in  this  city.  Mr.  Ward 
spoke  as  the  representative  of  the  officers  of  the  company,  who,  he  said, 
while  they  "  did  not  intend  to  belittle  the  credit  due  to  Mr.  Marconi,"  for 
the  advancement  he  has  made  in  the  field  of  wireless  telegraphy,  believed 
that  submarine  cables  would  hold  their  supremacy,  even  should  wireless 
telegraphy  "  ever  extend  beyond  its  present  experimental  stage  as  regards 
trans-Atlantic  or  other  long-distance  transmissions."  Mr.  Ward  added: 

"  Our  shareholders  must  not  overlook  the  fact  that  it  has  taken  the 
Commercial  Cable  Company  and  its  land  line  system  some  seventeen 
or  eighteen  years  to  perfect  their  organization  for  the  distribution  and  col- 
lection of  telegrams  throughout  the  United  States  and  the  rest  of  the  world. 
Assuming  that  the  Marconi  system  should  become  perfected  so  that  it 
could  really  compete  in  a  commercial  sense,  and  commercial  requirements 
are  very  exacting,  it  is  fair  to  say  that  it  would  take  as  many  years  to  put 
the  Marconi  system  in  a  position  that  would  enable  it  to  serve  the  public. 
Messages  are  now  transmitted  across  the  Atlantic  and  answers  received  in 
two  and  three  minutes.  A  message  experiencing  a  delay  of  ten  or  fifteen 
minutes  means  the  defeat  of  the  object  of  the  sender.  A  most  important 
point  is  the  fact  that  95  per  cent  of  the  Atlantic  messages  are  expressed  in 
code  or  cipher  language,  the  words  or  ciphers  having  no  connected  mean- 
ing. The  words  or  cipher  groups  frequently  only  differ  from  each  other  in 
single  letters,  yet  they  have  widely  different  meanings,  and  an  error  in  the 
transmission  of  one  of  their  letters  might  have  disastrous  consequences. 
These  are  some  of  the  commercial  exactions  or  demands  made  upon  the 
telegraphs.  No  one  as  yet  even  has  pretended  that  the  speed  with  which 
messages  may  be  transmitted  by  wireless  apparatus  even  approaches  the 
speed  of  the  aerial  or  submarine  wire. 

The  company's  net  earnings  for  the  year  ended  December  31,  1901, 
amounted  to  $2,2 59,897,  a  decrease  of  $19,770  compared  with  1900.  After 
payment  of  interest  and  dividends  there  was  a  balance  of  $409,538,  against 
$493,003  in  1900." 


128  WIRELESS    TELEGRAPHY. 

Marconi's  Belief.  —  Herewith  is  reprinted  by  permission 
from  the  Century  Magazine,  Marconi's  own  contention. 
This  item  was  published  about  the  same  time  as  that  of 
Vice-President  Ward  of  the  Cable  Company : 

"  Mr.  Marconi  believes  that  his  system  may  become  a  formidable  com* 
petitor  against  the  ocean  cables.  To  compete  on  land  is  not  so  easy, 
as  the  lines  there  cost  only  one  hundred  dollars  a  mile,  whereas  the  cables 
cost  one  thousand  dollars  a  mile,  and  require  expensive  steamers  to  repair 
and  maintain  them.  A  transatlantic  cable  represents  an  initial  outlay  of  at 
least  three  million  dollars,  besides  the  cost  of  its  maintenance.  A  Marconi 
station  can  be  built  for  sixty  thousand  dollars.  Three  of  these,  bringing 
the  two  worlds  into  contact,  will  cost  only  one  hundred  and  eighty  thousand 
dollars,  while  their  maintenance  should  be  insignificant.  What  his  success 
will  mean  can  be  best  grasped  by  considering  the  extent  of  the  property 
which  would  be  displaced  thereby,  although  it  is  only  since  August  5th, 
1858,  that  the  first  Atlantic  cable  was  laid.  There  are  now  fourteen  laid 
along  the  Atlantic  bed,  and  in  the  whole  world  seventeen  hundred  and  sixty- 
nine  telegraph  cables  of  various  sizes,  with  a  total  length  of  almost  one 
hundred  and  eighty-nine  thousand  nautical  miles,  enough  to  girdle  the 
earth  seven  times.  These  require  a  great  number  of  ocean-going  cable 
steamers  for  their  laying  anal  repairs,  and  while  the  total  value  of  the  cables 
cannot  be  easily  computed,  it  is  known  to  be  a  fact  that  British  capitalists 
have  one  hundred  million  dollars  invested  in  cable  stocks." 

Marconi  has  said  to  his  English  stockholders  that 
whereas  the  speed  of  the  submarine  cable  is  directly 
affected  by  length  of  transmission,  the  wireless  system  is 
not  in  the  least  affected  by  distance.  That  "  it  is  just  as 
easy  to  work  at  high  speed  across  the  Atlantic  or  Pacific 
as  to  work  across  the  English  Channel."  He  is  confident 
of  establishing  direct  communication  between  England  and 
New  Zealand.1  He  says  that  the  curvature  of  the  earth 
does  not  affect  the  signals,  and  that  ultimately  he  will  be 
able  to  send  them  all  around  the  world. 

Speed  of  Transmission  over  Ocean  Cables.  —  Over  the 
German  Cable  from  New  York  to  the  Azores,  two  sets  of 

1  See  chart,  Fig.  39,  p.  124. 


THE   COMPARATIVE    MERITS.  129 

signals  in  opposite  directions  are  simultaneously  sent  at  a 
rate  of  about  seventy  words  per  minute  for  each  circuit  of 
a  duplex  transmission,  making  a  total  of  one  hundred  and 
forty  words.  This,  it  is  said,  is  the  best  that  is  done  over 
any  long  submarine  conductor.  The  principal  limiting 
factor  in  this  signaling  is  a  delaying  influence  due  to 
electrostatic  capacity.  Professor  Pupin  of  Columbia  Uni- 
versity, who  has  exhaustively  investigated  this  subject,  has 
pointed  out  that  electrostatic  capacity,  being  a  storage  of 
power,  is  an  advantage  rather  than  a  detriment  if  properly 
controlled ;  and  in  pursuance  of  his  plans  for  such  control,  it 
is  reported  that  the  Bell  Telephone  Company  has  equipped 
three  circuits  from  New  York  to  Chicago  with  "  Pupin  Coils," 
and  that  the  results  are  an  increase  in  the  efficiency  of  speech- 
communication  equivalent  to  one  hundred  per  cent. 

Professor  Pupin  is  sanguine  that  equally  good  results 
will  follow  a  similar  treatment  of  ocean  cables,  but  there  is 
no  way  of  demonstrating  this  fact  in  actual  practice  except 
by  the  construction  of  a  new  cable  in  conformity  with  his 
design.  He  has  been  quoted  in  newspaper  paragraphs  as 
saying  that  the  ultimate  possibility  in  submarine  telegraphy 
is  a  rate  of  one  thousand  words  per  minute  ;  and  while  it 
may  be  feasible  to  attain  this  speed  it  seems  that  condi- 
tions other  than  those  connected  with  induction  will 
require  for  such  rapid  work  both  a  larger  conductor  and 
an  increased  mass  of  insulating  material,  thus  entailing  an 
expense  in  construction  which  may  prove  prohibitive ;  and 
that  a  safer  estimate  of  probable  future  speed  is  five  hun- 
dred words  per  minute. 

Progressive  Invention  in  Cable  Apparatus.  —  It  may  be 

said  also  that  there  is  progressive  invention  in  cable  appa- 


130  WIRELESS   TELEGRAPHY. 

ratus.  Foresio  Guarini,  an  Italian  scientist  of  repute  in 
the  field  of  wireless  telegraphy,  has  suggested  the  coherer 
as  a  device  to  be  used  in  multiplexing  ocean  cables  by 
means  of  electrical  resonance.  Chemical  telegraphy,  here- 
inafter explained,  may  also  be  mentioned  in  this  connection. 
The  foregoing  suggestions  will  serve  to  point  the  fact  that 
although  etheric  transmission  has  undoubtedly  come  to  stay, 
the  possibilities  of  wave  propagation  through  copper  still 
offer  alluring  fields  of  research. 


WIRELESS    TELEGRAPHY    OVERLAND. 

Hertzian-wave  signaling  overland,  though  still  in  em- 
bryo, will  undoubtedly  become  an  important  factor. 
Marconi  believes  a  thousand  miles  in  one  span  to  be  a 
possible  transmission.  Guarini  has  been  somewhat  suc- 
cessful in  devising  automatic  repeaters  which  may  double 
or  treble  such  a  span.  Fessenden  predicts  that  a  circuit 
will  eventually  be  worked  from  New  York  to  Chicago. 

A  difficulty  in  making  the  comparison  between  wave 
and  wire  signaling  overland  arises  from  the  fact  that  the 
land  telegraph  systems  with  wires  seem  to  be  far  behind 
their  possibilities ;  which  is  to  say  that  the  telegraph  com- 
panies do  not  begin  to  do  what  they  might  ;  and  in  order 
to  present  an  intelligent  view  it  is  thought  best  to  explain 
at  some  length  the  present  situation  of  commercial  tele- 
graphy on  land. 

Controversy  in  the  Electrical  World.  — There  has  re- 
cently occurred  in  the  correspondence  department  of  the 
Electrical  Worlds  controversy  concerning  the  attitude  of 


THE    COMPARATIVE    MERITS.  131 

the  Western  Union  Telegraph  Company.  This  happening 
is  fortunate  in  that  the  participants  are  representative  men 
and  have  definitely  announced  their  opinions.  Professor 
Pupin  had  published  a  letter  which  virtually  stated  that  the 
officials  of  the  Western  Union  Telegraph  Company  were 
impervious  to  suggestions  from  inventors  or  scientists. 
The  Electrical  World  editorially  commenting  upon  this 
letter  took  the  ground  that  the  telegraph  authorities,  as 
compared  with  those  in  other  electrical  professions,  had 
been  noticeably  backward  in  developing  their  art.  The 
engineer  of  the  Western  Union  Company  replied  that  Pro- 
fessor Pupin 's  lack  of  practical  experience  in  telegraphy 
probably  accounted  for  his  misapprehension. 

The  Morse   System He  also  said  that  nothing   had 

ever  been  found  to  equal  what  telegraphers  call  "  Morse," 
a  term  used  to  define  the  method  of  reading  signals  by 
sound  which  renders  it  possible  to  write  down  a  message 
as  it  is  received,  the  telegram  at  the  receiving  end  being 
ready  for  delivery  as  soon  as  the  sending  operator  has  fin- 
ished his  work.  It  was  further  said  that  in  times  of  emer- 
gency and  for  some  purposes  the  Wheatstone  system  had 
value. 

Speed  of  Quadruplex The  engineer  of  the  Postal  Tel- 
egraph Company  gave  some  interesting  data  as  to  trans- 
mission by  Quadruplex  (a  species  of  "Morse")  between 
New  York  and  Boston,  by  which  it  appears  that  the  average 
number  of  words  sent  over  one  wire  by  four  operators  is 
four  thousand  nine  hundred  and  fifty  per  hour,  or  a  little 
less  than  twenty-one  words  per  minute  per  sender,  or 
eighty-four  words  per  minute  per  wire.  It  may  be 


132  WIRELESS    TELEGRAPHY. 

\ 

explained  that  in  doing  this  work  eight  men  are  employed, 
four  in  sending  and  four  in  receiving. 

A  circuit  between  Boston  and  New  York,  however,  does 
not  furnish  the  most  essential  data,  for  it  is  but  two  hun- 
dred and  fifty  miles  in  length.  The  great  telegraphic 
highways  are  the  wires  between  New  York  and  Chicago, 
which  are  a  thousand  miles  long.  Upon  these  circuits  the 
quadruplex  rate  is  likely  to  be  nearer  to  sixty  words  per 
wire  per  minute ;  but  for  the  purposes  of  comparison  we 
may  use  the  data  given  at  eighty  words,  as  it  is  certain  that 
this  rate  may  not  be  exceeded. 

The  "Postal"  engineer  also  stated  that  the  public  is  not 
finding  fault  with  the  present  telegraphic  service,  to  which 
statement  the  reply  may  be  made  that  the  public  is  not 
fully  enlightened.  He  further  stated  that  the  night  or 
half-rate  traffic  "  is  naturally  limited  by  reason  of  the  splen- 
did mail  facilities  between  our  principal  cities." 

Mail  Service Following  are  actual  facts  in  regard  to 

mail  service  : 

To  transport  a  letter  from  a  street  box  at  I25th  St.  and 
8th  Avenue,  New  York  City,  to  39th  Street  and  Cottage 
Grove  Avenue  in  Chicago,  requires  forty-five  hours  ;  con- 
sequently the  securing  of  an  answer  to  an  inquiry  by  such 
means  requires  more  than  four  futl  days. 

A  person  in  the  business  district  of  St.  Louis  desiring  to 
send  a  letter  to  New  York  at  two  in  the  afternoon  may 
just  as  well  mail  the  letter  at  midnight.  A  letter  regis- 
tered on  Thursday  afternoon  in  St.  Louis,  with  full  postage, 
was  not  delivered  in  the  business  district  of  New  York 
City  until  Monday  morning. 

First  class  mail  matter  deposited  in  the  Post  Office  in 


THE    COMPARATIVE    MERITS.  133 

Detroit,  Michigan,  at  six  in  the  afternoon  of  Thursday, 
will  not  be  delivered  down  town  in  New  York  until  Satur- 
day morning. 

Between  the  service  just  described  for  two  cents  and  the 
day  rate  of  forty  cents,  and  night  rate  of  thirty  cents  for 
ten  word  telegrams,  the  telegraph  companies  have  never 
been  able  to  see  an  opportunity  for  employing  at  night 
their  idle  wires. 

DIFFERENT    TYPES    OF    TELEGRAPH    APPARATUS. 

Besides  the  "Morse,"  there  is  telegraphic  apparatus 
known  as  the  "  Wheatstone,"  in  which  a  paper  ribbon  is 
first  perforated  and  then  sent  through  a  machine,  recording 
at  the  distant  end  with  ink  marks  upon  paper  tape  ;  the 
total  speed  of  two  sides  of  a  "duplexed  Wheatstone"  is 
about  two  hundred  words  per  wire  per  minute. 

There  is  also  the  Buckingham  page-printer,  which  first 
perforates  a  tape  by  means  of  a  device  like  a  typewriting 
machine,  feeds  the  messages  through  a  transmitting  ma- 
chine, and  produces  at  the  distant  end  typewritten  copies 
at  one  hundred  words  per  wire  per  minute. 

Another  device  is  the  Murray  page-printer,  which  practi- 
cally accomplishes  the  same  results  as  the  Buckingham 
and  attains  about  the  same  speed. 

Another  and  recent  device  is  the  Rowland  octoplex,  by 
which  eight  circuits  are  worked  over  one  wire,  each  circuit 
transmitting  thirty  words  per  minute,  a  total  of  two  hun- 
dred and  forty  words  per  wire  per  minute.  The  sending 
is  done  by  manipulating  typewriters,  typewritten  copies 
being  automatically  produced  at  the  receiving  station. 

It  is  said  that  the  Wheatstone  and  Buckingham  appa- 


134 


WIRELESS    TELEGRAPHY. 


ratuses  are  both  regularly  employed  by  the  Western  Union 
Telegraph  Company,  but  the  latter  system  was  not  men- 
tioned by  the  company's  engineer  in  the  Electrical  World 
controversy.  If  the  Murray  is  in  business  use  that  fact  is 
not  known  to  the  writer.  The  Rowland  octoplex  is  said 
to  be  employed  in  Germany. 

All  of  these  machines  are  complex  in  detail  and  costly 
to  construct.  If  there  be  considered,  however,  the  total 
investment  of  money  in  a  copper  wire  one  thousand  miles 
long  and  weighing  perhaps  four  hundred  pounds  per  mile, 
together  with  the  cost  of  planting  poles,  of  attachments  to 
those  poles,  and  the  expense  of  patrol  and  maintenance, 
the  claims  of  inventors  of  telegraphic  machines  that  their 
apparatuses  will  pay  for  themselves  in  a  short  time  seems 
well  founded.  Either  the  Buckingham  or  Murray  page- 
printers,  or  the  Rowland  octoplex,  are  rated  at  a  speed 
much  greater  than  that  of  quadruplexed  Morse.  All  of 
them  save  nearly  fifty  per  cent  in  operating  labor. 

The  officials,  however,  are  obdurate,  and  while  the  equip- 
ment of  perhaps  one  wire  with  a  new  device  is  occasionally 
allowed,  the  experiment  seldom  extends  any  further.  The 
result  of  such  policy  in  the  past  has  produced  a  great  array 
of  abandoned  machinery.  After  each  trial,  officials,  engi- 
neers, and  operating  force  are  further  strengthened  in  their 
admiration  for  the  true  and  the  tried  ;  and  the  disappointed 
inventors  claim  that  to  all  arguments  there  is  the  same 
response,  and  to  all  appeals  the  same  denial,  —  "  There  is 
nothing  like  Morse." 

Morse  Best  Adapted  to  Certain  Classes  of  Traffic.  —  No 

one  denies  that  for  the  class  of  service  that  transmits  orders 
from  the  New  York  Produce  Exchange  to  the  Chicago 


THE    COMPARATIVE    MERITS.  135 

Board  of  Trade  it  seems  impossible  to  find  a  substitute  for 
Morse.  It  is  said  that  to  the  telegraphers  in  the  Chicago 
Trade  Room  even  a  typewriting  machine  is  less  facile  than 
the  pen.  They  write  upon  a  blank,  using  copying  ink ; 
when  the  message  has  been  written,  a  moist  piece  of  paper 
is  laid  over  the  blank,  the  two  are  then  fed  between  the 
rubber  rollers  of  a  wringer,  and  there  is  quickly  in  hand 
the  original  message,  which  may  be  handed  the  consignee, 
and  an  impression  copy  for  the  company's  files. 

There  are  classes  of  business  which  require  the  same 
rapidity  of  delivery  as  do  those  of  the  grain  and  stock 
brokers,  and  for  which  Morse  seems  best  adapted.  There 
is,  however,  a  traffic  that  comes  from  the  general  public 
which  is  poorly  handled.  It  is  not  so  much  the  way  this 
class  of  business  is  being  transmitted  with  present  facilities 
as  a  matter  of  what  might  be  done  with  other  and  better 
devices  and  with  the  lower  tariffs  those  devices  would 
warrant. 

The  charges  for  sending  miscellaneous  telegrams  are  the 
same  as  for  those  of  the  preferred  class.  Under  favorable 
conditions  the  telegraph  companies  may  transmit  an  unpre- 
f erred  message  fairly  well ;  but  if  there  be  rain  or  wind  or 
excitement  in  Wall  Street,  or  an  election,  or  a  political  con- 
vention, the  wires  are  crowded ;  and  having  thus  to  contend 
against  frequent  delays  and  high  tariffs  it  is  no  wonder 
that  the  number  of  these  unfavored  communications  is 
comparatively  small.  As  Mr.  Delany,  in  one  of  the  letters 
of  the  recent  discussion,  has  pointed  out,  there  is  no  elas- 
ticity, no  reserve  power  in  the  present  telegraph  service. 
For  the  class  of  business  just  described,  low  rates  and  the 
adoption  of  some  of  the  new  possibilities  in  multiplex  or  in 
chemical  telegraphy  would  undoubtedly  increase  the  re- 


136  WIRELESS   TELEGRAPHY. 

ceipts  of  the  telegraph  companies  and  prove  as  well  a  boon 
to  the  public. 

Chemical  Telegraphy.  —  Almost  coeval  with  Professor 
Morse's  inventions  are  those  of  Alexander  Bain,  who  de- 
clared as  long  ago  as  1845  that  by  the  chemical  method 
he  could  transmit  two  thousand  words  per  minute.  A 
system  based  on  this  principle  was  tried  by  the  Atlantic 
and  Pacific  Telegraph  Company  in  1875.  Its  officials 
made  two  mistakes,  first  ordering  that  it  be  used  for  all 
kinds  of  traffic,  and  then  that  its  use  be  entirely  discontin- 
ued. In  the  eighties  the  American  Rapid  Company  tried 
the  system  again,  but  that  company  was  unsuccessfully 
financed  and  soon  collapsed. 

The  essential  principle  of  chemical  telegraphy  is  the 
fact  that  an  impression  is  made  whenever  a  current  of  elec- 
tricity passes  from  a  metallic  point  resting  upon  chemically 
treated  moist  paper  to  a  conductor  which  connects  with  a 
part  of  the  same  circuit  from  another  point  on  the  paper. 
The  action  is  electrolytic.  A  copper  point  leaves  a  red 
mark,  an  iron  one  a  deep  blue.  The  number  of  signals  is 
governed  by  the  volume  of  current,  by  the  time  of  exposure, 
and  to  some  extent  by  the  electrostatic  capacity  of  the 
conductor  connecting  the  sending  and  receiving  stations. 
It  may  be  expressed  by  the  equation 

FT 
N  - 

"RK 

where  N  is  the  number  of  signals  per  unit  of  time,  E  the 
electromotive  force,  T  time,  R  resistance,  and  K  capacity. 
While  the  author  is  not  exactly  informed  as  to  quantita- 
tive results,  it  is  safe  to  say  that  one  five-thousandth  of  an 
ampere  flowing  from  an  iron  point  and  impressed  upon  the 


THE   COMPARATIVE    MERITS. 


137 


sensitized  paper  for  one  second  of  time  will  leave  a  distinct 
mark  ;  and,  conversely,  that  one-twentieth  ampere  unim- 
peded by  capacity  is  sufficient  current  to  produce  two 
thousand  words  per  minute,  each  word  requiring  from  ten 
to  twenty  marks. 

Description  of  Chemical  Telegraph  Apparatus.  —  Fig.  40 
is  a  diagrammatic  view  of  a  chemical  telegraph  circuit,  P 
being  a  source  of  current  supply  with  one  polarity,  and  N  a 
second  source,  having  a  polarity  the  reverse  of  the  first. 
B  and  B'  are  brushes  terminating  respectively  conductors 


Fig.  40. 

from  P  and  N.  B"  and  B"  '  are  brushes  on  the  surface  of 
the  sending  tape  ST  which  are  brought  into  contact  with 
B  and  B'  by  reason  of  the  holes  in  the  paper  being  moved 
past  them  whenever  the  paper  is  pulled  along  by  friction 
rollers  FF.  The  yoke  y  is  of  conducting  material,  and 
consequently  B"  and  B"  '  are  electrically  one  piece  which 
is  connected  to  the  line.  At  the  far  station  RT  is  the 
chemically  treated  receiving  tape,  and  resting  upon  it  is  an 
iron  pen  C  which  is  joined  by  insulating  material  x  to  the 
platinum  faced  strip  C'  called  the  spacing  pen. 


WIRELESS   TELEGRAPHY. 

Operation  of  Chemical  Telegraph.  —  Whenever  a  contact 
is  made  oetween  brush  B  and  the  line  by  reason  of  the 
passing  of  one  of  the  lower  holes  in  tape  ST,  current  flows 
across  RT  from  C  to  C'  and  colors  the  paper.  After  brush 
B  has  passed  a  hole,  the  charge  of  electricity  which  has 
become  stored  in  the  line  flows  to  earth,  and  this  secondary 
flow  of  current  tends  to  prolong  the  mark.  Thus  the 
horizontal  distance  between  a  lower  and  an  upper  perfora- 
tion impresses  upon  the  sensitized  paper  either  a  long  or  a 
short  mark  according  as  the  distance  between  any  lower 
opening  and  its  relative  upper  opening  is  long  or  short ;  for 
whenever  brush  B'  is  presented  to  line,  it  neutralizes  the 
current  flowing  from  C  to  C',  and  the  pen  C  ceases  to  color 
the  paper. 

Neutralizing  Electrostatic  Effects.  —  The  system  of 
positive  and  negative  presentations  is  an  improvement  upon 
the  earlier  methods,  which  used  current  of  one  polarity 
only.  Under  the  plan  just  illustrated,  inductive  influence 
is  partly  neutralized ;  and  by  another  and  very  simple 
contrivance  in  connection  with  the  apparatus,  the  details 
of  which  the  author  is  not  at  liberty  to  make  public, 
electrostatic  capacity  seems  to  be  under  absolute  control. 

Speed.  —  The  speed  of  the  chemical  telegraph  is  marvel- 
ous. Mr.  Delany,  the  chief  exponent  of  that  kind  of 
transmission,  has  succeeded  in  recording  in  a  laboratory, 
and  over  an  artificial  line  the  equivalent  of  an  ordinary 
telegraphic  circuit  one  hundred  and  twenty-five  miles  in 
length,  eight  thousand  words  per  minute.  The  author  has 
seen  an  initial  force  of  one  hundred  and  ten  volts  transmit 
one  thousand  words  per  minute  over  an  artificial  line  hav- 


THE  COMPARATIVE    MERITS.  139 

ing  the  resistance  and  electrostatic  capacity  of  a  circuit 
between  New  York  and  Chicago.  There  is  no  reason  why 
machines  should  not  be  devised  by  which  two  thousand 
words  per  minute  may  be  sent  with  one  hundred  volts ;  nor 
is  there  any  insuperable  obstacle  to  the  use  of  five  hundred 
volts.  Indeed  the  sending  ten  thousand  words  per  minute 
over  a  copper  wire  a  thousand  miles  long  weighing  four 
hundred  pounds  per  mile  is  a  possibility  of  the  present 
development.  Chemical  transmission  is  now  used  by  the 
Pennsylvania  Railroad  Company  between  Philadelphia  and 
Altoona,  and  over  the  circuit  employed,  Mr.  Delany  has 
made  a  record  of  thirteen  hundred  words  per  minute.  The 
line  measures  in  resistance  about  fourteen  hundred  ohms, 
and  is  partly  of  iron  wire. 

There  has  been  a  plan  for  perforating  paper  tape  by  the 
manipulation  of  a  Morse  Key ;  and,  as  the  action  of  a 
telegraph  key  is  simply  a  down-and-up  motion  of  a  pivoted 
lever,  this  action  may  be  reproduced  at  a  considerable 
distance  from  the  location  of  the  sending  operator.  At  the 
distant  point  the  tape  may  be  fed  into  a  transmitter,  and  it 
may  be  reproduced  by  chemical  signals  over  a  second 
circuit. 

To  illustrate  the  plan  of  operation,  a  telegram  from  New- 
ark, New  Jersey,  for  delivery  at  Milwaukee,  Wisconsin, 
under  present  conditions  would  be  sent  by  Morse  from 
Newark  to  the  main  office  in  New  York  City,  thence  by 
quadruplex  to  Chicago,  thence  by  Morse  to  Milwaukee. 
By  the  perforator  and  chemical  telegraph  the  Newark 
operator  could  make  in  the  main  office  at  New  York  a 
tape  which  would  be  used  to  transmit  the  message  from 
New  York  to  Chicago,  where  it  would  appear  in  the  form 
of  Morse  signals  on  a  moist  paper  ribbon,  and  this  might 


UNIVERSITY 


140  WIRELESS   TELEGRAPHY. 

be  handed  to  an  operator  in  Chicago  to  be  sent  to  Mil- 
waukee by  Morse. 

In  the  first  method  the  number  of  sets  of  human  heads 
and  hands  occupied  with  the  message  is  six ;  in  the  latter 
three,  and  consequently  this  latter  presents  just  one-half 
the  chance  for  errors.  Moreover,  in  the  actual  time  of 
passage  the  gain  is  considerable.  The  saving  in  plant,  al- 
lowing to  the  second  method  five  thousand  words  per 
minute,  is  as  sixty  to  one  over  quadruplexed  Morse ;  and 
would  be  as  forty  to  one  over  any  of  the  type-printers. 

So  much  space  has  been  given  to  the  chemical  system 
because  of  its  development.  It  is  wonderful  that  an  organ- 
ization so  complete  could  have  been  perfected  without  the 
experience  that  comes  from  daily  use  ;  and  more  wonder- 
ful still,  that  having  been  thus  perfected,  it  should  be 
entirely  neglected  by  the  telegraph  companies. 

Other  Means  of  Rapid  Signaling.  —  There  are  undevel- 
oped means  of  signaling,  however,  which  to  experts  in 
wireless  telegraphy  seem  certain  of  future  attainment. 
Both  Marconi  and  Fessenden  are  looking  forward  to  ma- 
chine transmission  at  a  speed  of  five  hundred  words  per 
minute,  and  they  are  also  hopeful  of  multiplexing  wireless 
circuits.  Many  of  the  obstacles,  however,  which  loom  up 
in  the  future  of  wireless  telegraphy  do  not  present  them- 
selves in  transmission  by  wire,  and  there  is  every  reason  to 
suppose  that  a  wire  may  not  only  be  multiplexed  many 
times,  but  that  each  of  the  phantom  circuits,  as  they  are 
called,  may  be  made  by  machinery  to  convey  some 
hundreds  of  words  per  minute  ;  always  with  more  certainty 
and  speed  than  without  the  wires. 

It  is  the  apparent  neglect  of  such  great  forces  for  which 


THE    COMPARATIVE    MERITS.  141 

the  telegraph  officials  are  held  accountable  by  those  ac- 
quainted with  the  facts.  Complication  may  not  be  urged, 
because  the  chemical  system,  for  example,  is  far  simpler, 
both  in  construction  and  operation,  than  is  either  the 
duplex  or  the  quadruplex  or  the  typewriter  devices.  The 
passage  over  a  single  wire  of  thousands  of  words  per  min- 
ute is  as  well  assured  as  is  wireless  telegraphy ;  and  if 
brought  into  regular  commercial  use  it  may  prove  a 
greater  public  benefit.  At  present  there  is  no  outlook  that 
etheric  signaling  overland  will  ever  attain  to  the  tremen- 
dous possibilities  of  telegraphy  with  wires. 


142 


WIRELESS   TELEGRAPHY. 


S 


NOMENCLATURE. 


PART  IV. 


APPARATUS. 

NOMENCLATURE. 

THE  art  which  forms  the  subject-matter  of  this  work 
is  young  and  its  nomenclature  limited.  "  Wireless  Tele- 
graphy" itself  but  a  negative  term  is  temporarily  supplying 
the  need  of  a  positive  designation.  Neither  "  radio-tele- 
graphy" nor  "wave-telegraphy"  nor  "etheric-transmission" 
satisfies.  "  Hertzian-wave  telegraphy  "  is  of  unwieldy 
length  and  lacks  euphony, 

No  single  word  suitably  denotes  every  kind  of  instru- 
mentality- affected  by  Hertzian  or  magnetic  waves. 
"  Detector "  has  been  used  in  another  sense.  Mr.  Tesla 
speaks  of  "  sensitive-devices  "  ;  Mr.  Fessenden  and  others 
of  a  "wave-responsive-device."  "  Responder "  is  too 
closely  identified  with  the  DeForest  system  to  be  ac- 
ceptable to  competitors.  "  Resonator,"  to  denote  a  receiv- 
ing device,  is  objectionable  on  account  of  its  alliterative 
and  structural  similarity  with  "  radiator,"  a  transmitter. 

Antenna  is  an  excellent  name  for  the  conducting  termi- 
nal that  ends  in  air  whenever  the  allusion  is  to  a  receiver 
of  waves ;  but  it  is  not  sufficiently  aggressive  to  express 
the  opposite  meaning.  Emitter  seems  a  good  term  for 
designating  anything  that  serves  to  send  impulses  outward. 
The  terminating  conductor,  however,  being  employed  both 


144 


WIRELESS    TELEGRAPHY. 


as  antenna  and  emitter,  the  necessity  appears  for  that 
which  denotes  both  uses.  Mr.  Fessenden  speaks  of  an 
aggregation  of  five  wires  as  a  "  harp."  When  the  condi- 
tions are  applicable,  "high  wire"  is  a  good  term,  but  not 
when  cylinders  or  cones  are  used.  The  writer  suggests  as 
a  comprehensive  title,  one  used  in  this  work,  "wave-gate." 
For  the  instrument  that  acts  bv  diverse  resistances  of 

J 

a  sensitive  device  and  thus  translates  the  signals  to  a  local 


Fig.  42.— Elevating  the  kite-supporting  wave-gate  at  Signal  Hill,  St.  Johns, 
Newfoundland,  December  12,  1901.— X  Marconi. 

and  more  powerful  circuit,  no  better  name  than  "relay" 
can  be  found  :  but  to  speak  in  that  connection,  of  a  "  rev 
ceiver,"  is  to  confuse  it  with  the  sensitive  device  itself. 

The  circuit  which  contains  a  radio-receiver  battery  and 
relay  has  occasionally  been  designated  "local,"  not  in- 
trinsically a  good  term,  and  the  less  acceptable  because  to 
telegraphers  it  implies  a  second  organization  in  contra- 
distinction to  the  connections  of  the  main  line. 


NOMENCLATURE.  145 

As  suggested  by  Mr.  Tesla's  "  sensitive-device,"  the 
train  of  apparatus  having  the  radio-receiver  for  one  ele- 
ment might  properly  be  denoted  the  "  sensitive  circuit," 
and  the  battery  which  actuates  the  relay  in  that  circuit 
the  "  closing  battery." 

For  the  wires  and  apparatus  in  series  with  the  relay 
points,  "  recording-circuit,"  and  for  the  energizing  element 
of  that  group,  "  recording  battery,"  are  designations  that 
should  be  clearly  understood. 

The  terms  "spark-producer,"  "oscillator,"  and  "oscil- 
lation-producer "  are  synonymously  applied  to  all  apparatus 
that  sends  electric  charges  across  the  spark-gap. 

"  Induction-coil,"  the  "  primary  "  and  "  secondary  "  which 
compose  it,  and  the  "key  "  used  to  bring  into  operation 
the  sparker,  are  terms  well  fixed  in  the  public  mind.  The 
contact  which  rapidly  opens  and  closes  in  the  primary 
circuit  is  happily  described  in  Marconi's  patents  as  the 
"  trembler-break." 

As  both  Professor  Lodge  and  Signor  Marconi,  partly  for 
the  purpose  of  broadening  their  patent  claims,  have  in- 
sisted that  both  the  earth  and  the  wave-gate  are  "  capa- 
cities," that  term  may  not  now  be  understood  as  confined 
in  meaning  to  a  condenser  or  to  a  Leyden  jar. 

TRANSMITTERS. 

Ruhmkorff  Coil.  —  Before  the  advent  of  wireless 
telegraphy  the  Ruhmhorff  Coil  was  the  standard  spark- 
producer.  Referring  to  Fig.  43  as  an  illustration  of  that 
coil,  it  may  be  described  as  follows : 

In  a  position  of  rest  the  contact  of  spring  T  is  in  touch 
with  that  of  upright  K.  By  the  closure  of  the  break  at 
switch  S,  battery  B  energizes  circuit  B-S-T-K,  causing 


146 


WIRELESS    TELEGRAPHY. 


the  iron  coil  I  to  become  magnetic.  The  iron  face  of 
spring  T  is  attracted  towards  coil  I,  but  as  the  movement 
forward  immediately  breaks  contact  at  a,  I  is  demagne- 
tized, and  the  spring  T  resuming  its  first  position  in  con- 
tact with  K,  coil  I  again  becomes  magnetized.  On 
account  of  the  quickly  changing  conditions  in  coil  I,  there 
occur  continuous  and  rapid  vibrations  at  point  a. 


Fig.  43- 

When,  however,  the  current,  after  being  made,  is  inter- 
rupted at  point  a,  there  takes  place  an  electric  discharge 
which  is,  in  effect,  a  flow  of  current  in  an  opposite  direc- 
tion to  the  charge  which  has  just  been  made.  This 
reverse  current,  though  of  high  pressure,  is  attenuated, 
and  has  much  less  magnetic  effect  on  the  coil  than  the 
initial  one.  It  tends,  however,  slightly  to  magnetize  coil 
I  at  a  time  when  that  coil  should  be  non-attractive :  and  it 


TRANSMITTERS. 


147 


is  also  true  that  the  high  pressure  generated  is  apt  to  burn 
the  contacts  at  a. 

The  function  of  condenser  C  is  to  give  back  its  charge 
with  the  same  energy  as  that  which  emanates  from  the  pri- 
mary coil,  thus  neutralizing  the  bad  effect  of  the  primary 
coil's  discharge.  It  is  seldom,  however,  that  the  adjust- 
ments of  the  two  forces  are  quite  in  balance,  and  conse- 
quently there  is  generally  more  or  less  imperfect  action  at  a. 

Marconi's  Spark-Producer. —  In  Marconi's  patent  1 1,913 
is  described  a  device  which  partially  obviates  the  difficulty 
of  corrosive  points,  in  that,  by  means  of  a  small  electric 
motor,  it  causes  one  of  the  points  of  the  vibrating  break 
continuously  to  revolve.  The  spark  in  this  patent  is  shown 
with  an  interposition  of  two  balls  in  the  center  in  an  ebonite 
casing.  The  distance  between  the  center  balls  is  one 
twenty-fifth  inch,  and  the  inside  distance  between  each  of 
the  terminating  electrodes  and  the  center  balls  one  and 
one-half  inches.  The  space  between  the  two  middle  spheres 
is  filled  with  vaseline 
oil.  It  is  said  that  Mr.  f8 

Marconi  afterward  dis- 
carded the  center 
globes  and  used  a  clear 
space  between  elec- 
trodes. 

A  Fessenden   Trans- 
mi  tter.  —  Fig.    44 
showsatrans- 
m  i  1 1  e  r    de- 
signed by  Mr.  Fig  44 


I48  WIRELESS   TELEGRAPHY. 

Fessenden,  the  patent  for  which  was  filed  December  1 5, 
1899.  A  distinctive  feature  is  the  condenser  18  bridging 
the  spark  gap  between  electrodes  4-4.  This  arrange- 
ment, the  inventor  says,  is  "  for  the  purpose  of  maintain- 
ing sustained  radiation,"  for  "this  shunt  circuit  by  reason 
of  its  capacity  stores  up  an  additional  amount  of  energy, 
and  when  a  spark  passes  across  the  gap,  since  the  sending 
conductor  can  radiate  energy  at  a  given  rate,  it  must 
continue  to  radiate  for  a  long  time  in  order  to  dissipate 
this  additional  stored  up  energy." 

a  A  similar  organization  is  shown  in  the  Marconi  patent 
676,332,  of  later  date  than  the  Fessenden.1 

Alternating  Current  Dynamo  Instead  of  Interrupter. - 

The  interrupter  in  the  primary  coil  of  a  direct  current 
sparking  appliance  being  difficult  of  control  with  currents 
of  high  potential,  it  is  the  practice  in  large  installations  to 
employ  steam  power  connected  with  an  alternating  current 
dynamo,  the  voltage  of  which  may  be  "stepped  up"  by 
transformers ;  and  where  steam  power  is  not  available,  but 
energy  is  had  from  storage  batteries,  as  in  field  operations, 
direct  current  from  the  batteries  may  be  made  to  turn  an 
electric  motor  by  which  an  alternating  current  dynamo  may 
bejkept  in  motion  to  furnish  the  primary  coil  with  energy 
to  supply  the  spark  gap. 

Fessenden  Dynamo  as  Direct  Emitter.  —  The  use  of  a 
dynamo  for  a  direct  emitter  without  the  spark  gap  is  shown 
in  Fessenden's  patent  706,737.  He  claims  that  he  is 
able  at  once  to  produce  a  continuous  train  of  radiant  waves 
jof  substantially  uniform  strength,  as  distinguished  from 

1  See  Fig.  37  in  Part  II. 


TRANSMITTERS.  149 

the  well-known  systems  wherein  the  spark-discharge  starts 
a  train  of  waves  of  rapidly  diminishing  power,  followed  by 
relatively  long  intervals  of  no  radia- 
tion. Fig.  45  is  a  diagram  from  the 
Fessenden  patent  where  i  is  a  short 
emitting  wave-gate  with  large  radia- 
ting surface,  2  a  tuning  inductance, 
3  an  alternating  current  dynamo  with 
an  earth  connection. 

Fig.  45- 

DeForest  Transmitter.  — The  tran- 
smitter of  the  DeForest  system  uses  an  alternating  cur- 
rent dynamo,  a  step-up  transformer  to  increase  the  vol- 
tage ;  and  discharges  across  a  gap  in  which  is  interposed 
a  detached  conductor.  The  discharging  electrodes  and 
the  interposed  member  are  of  the  same  shape  and  size, 
being  disks  of  metal  about  one-quarter  inch  thick,  and 
upon  the  sides  or  faces  about  one  and  one-quarter  inches 
in  diameter.  The  spark  gaps  upon  each  side  of  the  middle 
disk  measure  about  one  sixty-fourth  inch. 

The  DeForest  experts  claim  that  with  electrodes  of  a 
surface  relatively  large  as  to  the  gap  they  get  a  "  fat  " 
spark,  and  that  such  a  spark  produces  better  results  at  the 
distant  or  responding  end  than  would  one  of  greater  inten- 
sity but  less  volume. 

A  Fessenden  Transmitter.  —  Figs.  46  and  47  are  repro- 
ductions from  drawings  in  one  of  Mr.  Fessenden's  patents, 
No.  706,641,  filed  November  5,  1901.  The  diagram  of 
curves,  Fig.  46,  is  a  graphic  representation  of  comparative 
efficiencies.  The  dots  on  horizontal  line  c  indicate  spark 
potential  in  inches,  the  vertical  line  d  radiation  or  effective 


ISO 


WIRELESS    TELEGRAPHY. 


Fig.  46. 


result,  b  is  an 
efficiency  curve 
which  shows 
results  obtain- 
ed under  usual 
conditions,  viz.: 
that  within  a 
certain  length 
of  spark,  about 
one  inch,  the 
resultant  radia- 
tion of  electromagnetic  waves  is  approximately  proportional 

to  the  length  of  spark  ;    but  that  to  increase  the  length  of 

spark  beyond  one  inch  will  result  in  no  practical  increase 

in    radiation.     The  line 

a    is  another   efficiency 

curve  which  is  employed 

to  demonstrate  that  with 

Mr.  Fessenden's  device, 

the  wave  force  d  is  ex- 
actly    proportional      to 

spark  gap  c  at  whatever 

length  the  latter  may  be 

prolonged. 

Referring  to  Fig.  47, 

10  is  a  rod  pointed  at 

its  lower  end,  surrounded 

by  an  insulating  sleeve 

n,    and    so    introduced 

into  the  chamber    7   to 

form    one    electrode    of 

the     spark    gap.      The  Fig*  47' 


TRANSMITTERS.  151 

other  electrode  is  the  bottom  plate  of  chamber  7,  and  thus 
one  of  the  discharging  terminals  is  a  point  4,  and  the 
other  a  disk,  5.  By  means  of  pump  8,  the  air  in  chamber 
7  is  increased  in  pressure.  It  is  found  that  when  a  certain 
critical  pressure  is  reached,  which,  for  instance,  may  be 
eighty  pounds  per  square  inch,  the  radiation  for  any  length 
of  spark  becomes  strictly  proportional  to  the  applied  force. 
The  term  "  radiation  "  in  the  foregoing  explanation,  and 
as  shown  by  the  height  of  vertical  line  d  of  the  curve  dia- 
gram, is  an  expression  of  an  applied  energy,  that,  if  doubled 
or  trebled,  doubles  or  trebles  the  distance  from  such  energy 
for  which  a  wave-responsive  device  may  be  made  to  indi- 
cate signals. 


152  WIRELESS   TELEGRAPHY. 


WAVE-RESPONSIVE-DEVICES. 

Considering  as  a  generic  term  either  "  sensitive-device," 
or  "wave-responsive-device,"  or  "radio-receiver,"  or  "de- 
tector," there  may  be  made  as  classifications  of  it  "coher- 
ers," "anti-coherers,"  "micro-radiophones,"  and  "mag- 
netic-radio-receivers." 

Coherers.  —  If  used  without  a  qualifying  word  or  prefix 
the  word  coherer  is  now  understood  to  indicate  that  form 
of  radio-receiver,  which,  being  normally  a  high  resistance, 
is,  under  the  influence  of  Hertzian-waves,  changed  to  a  low 
resistance,  becoming  relatively  a  conductor,  and  remaining 
electrically  conductive  after  the  subsidence  of  the  wave 
effect  unless  restored  to  its  original  state  of  resistivity  by 
some  sort  of  mechanical  impact. 

Filings  Tube  of  Calzecchi-Onesti.  Decoherence  by  Re- 
volving  So  long  ago  as  1886,  Professor  Calzecchi- 
Onesti  placed  copper  filings  between  two  brass  plates  and 
changed  the  electrical  property  of  the  filings  from  a  state 
of  high  resistance  to  one  of  low  resistance  by  passing 
through  them  the  secondary  impulse  that  occurs  when  an 
electric  circuit  is  broken.  Afterward  to  facilitate  decoher- 
ence  he  inclosed  the  filings  in  a  revoluble  glass  tube. 

Branly's  Filings.  Tube  Decoherence  by  Tapping. — 
Branly,  1891,  discovered  that  the  filings  could  be  rendered 
conductive  by  the  passage  of  electric  sparks  across  an  air- 
gap  in  their  vicinity,  and  that  they  could  be  decohered  by 
a  slight  jar. 


WAVE-RESPONSIVE-DEVICES.  153 

Lodge  and  Fitzgerald  Needle  and  Tin-Foil.  —  Dr.  Lodge, 
in  conjunction  with  Mr.  Fitzgerald,  made  a  coherer  by 
causing  the  point  of  a  sewing-needle  to  rest  upon  a  strip  of 
tin-foil.  Later,  this  device  was  elaborated  by  contacting 
the  needle  point  with  a  flat  spring  which  was  fixed  within 
a  clamp,  the  degree  of  pressure  between  point  and  spring 
being  regulated  by  adjusting  screws. 

Branly's  Tripod  of  1902.  —  Professor  Branly  in  1902 
placed  a  tripod  having  sharp  steel  points  slightly  oxidized 
upon  a  polished  plane  steel  plate.  A  current  of  electricity 
passing  from  tripod  to  plate  is,  under  normal  conditions, 
subjected  to  a  high  resistance.  This  resistance  is  greatly 
•diminished  by  Hertzian- wave  effect,  and  may  be  re-estab- 
lished by  so  arranging  a  recording  instrument,  that  imme- 
diately after  the  wave  effect  is  discontinued,  it  will  jar  the 
plate. 

Tesla's  Filings  Tube.  Decoherence  by  Inversion.  —  In 
his  patent  No.  613,819,  Mr.  Tesla  describes  quite  minutely 
a  form  of  filings  coherer  which  is  decohered  by  being 
turned  end  for  end,  its  position  of  rest  being  vertical.  He 
makes  the  particles  as  nearly  as  possible  alike  in  size, 
weight,  and  shape,  having  special  tools  to  fashion  them ; 
and  then  oxidizes  them  uniformly  by  placing  the  grains  for 
a  given  time  in  an  acid  solution  of  predetermined  strength. 
He  prefers  not  to  rarefy  the  atmosphere  within  the  tube, 
since  by  rarefaction  it  is  rendered  less  constant  in  dielec- 
tric property.  He  recommends  an  air-tight  inclosure  and 
a  rigorous  absence  of  moisture.  In  another  patent  he 
specifies  decoherence  by  continuous  revolution,  instead  of 
by  inversion,  of  the  glass  tube. 


154  WIRELESS   TELEGRAPHY. 

The  "  Silver  "  Coherer — So  far  as  is  known  by  records 
of  practical  tests  the  most  sensitive  type  of  the  class  under 
consideration  is  the  "silver"  coherer.  It  is  carefully 
described  in  the  American  reissue  patent  No.  11,913  of 
Marconi.  Briefly  the  tube  is  one  and  one-half  inches  in 
length,  and  one-twelfth  inch  internal  diameter.  Within 
it  are  tightly  plugged  two  pieces  of  silver  wire,  each  one- 
fifth  inch  long.  The  space  between  these  plugs  at  center 
is  one-thirtieth  inch.  This  minute  space  contains  a  pow- 
der composed  of  ninety  per  cent  of  nickel  filings,  and  ten 
per  cent  of  silver  filings.  The  grains  are  as  large  as  may 
be  produced  with  a  coarse  file,  and  are  coated  with  an 
almost  imperceptible  globule  of  mercury.  The  tube  must 
be  sealed.  A  perfect  vacuum  is  not  essential,  but  is  de- 
sirable, and  one  of  one-thousandth  atmosphere  has  been 
used.  Sensitiveness  to  waves  may  be  increased  by  using 
a  greater  percentage  of  silver  grains  in  the  powder,  or  by 
decreasing  the  distance  between  the  silver  stops. 

ANTI-COHERERS. 

Hertz  Detector.  —  The  first  radio-receiver  in  which  cause 
and  effect  were  observed  and  recognized 
was  devised  by  Hertz  in  1886.  It  con- 
sisted of  a  piece  of  wire,  Fig.  48,  bent  into 
circular  form,  a  small  disconnecting  gap 
being  left  in  its  circumference.  If  this  de- 
vice were  suspended  at  some  distance  from 

Fig.  48. 

a  sparking  Ruhmkorff  Coil,  there  being 
no  tangible  connection  between  the  coil  and  the  circlet  of 
wire,  minute  sparks  could  be  seen  to  fly  across  the  air-gap 
in  the  wire. 


WAVE-RESPONSIVE-DEVICES.  155 

Righi  Detector.  —  Professor  Righi  obtained  similar  action 
by  holding  at  a  few  feet  from  a  spark-producer  a  sheet  of 
glass  covered  with  tin-foil,  the  metal  being  separated  by  a 
fine  diamond  point  into  several  longitudinal  bands.  Action 
at  the  electrodes  of  the  induction  coil  resulted  in  sparking 
from  band  to  band  over  the  gaps  in  the  tin-foil. 

In  1899  a  German  scientist  discovered  that  by  placing  a 
drop  of  water  upon  the  slit  formed  by  the  tin-foil  edges  of 
the  Righi  bands,  a  very  sensitive  wave-detector  was  pro- 
duced. 

It  is  said  the  organizations  just  described  differ  from  a 
coherer,  in  that  the  action  of  waves  causes  their  electrical 
resistance  to  increase,  an  effect  exactly  opposite  to  that  set 
up  in  the  coherer  proper.  They  are,  therefore,  named 
"  anti-coherers,"  and  differing  in  principle,  are  declared  not 
to  be  subordinate  to  any  patent  claims  which  may  cover  a 
coherer  method.  There  is  a  report,  however,  that  the 
Marconi  Company,  presumably  on  the  ground  that  the 
alleged  anti-coherer  is  an  "imperfect  contact,"  is  preparing 
to  bring  action  for  infringement  against  a  competitor  using 
an  anti-coherer. 

DeForest    Responder The  DeForest  "responder"  is 

the  most  prominent  type  of  anti-coherer.  Fig.  49  illus- 
trates the  receiving  apparatus  in  which  A  and  A'  are  two 
small  brass  rods,  or  wires,  connected  respectively  to  the 
wave-gate  and  to  the  earth.  D  and  D  are  hard  rubber 
tubes,  into  which  is  fitted  the  glass  tube  C.  F  and  F'  in- 
dicate the  position  of  adjusting  screws  which  serve  to 
make  greater  or  less  the  width  of  the  gap  which  occurs  at 
G  between  electrodes  A  and  A'.  B  is  a  battery,  gen- 
erally of  two  or  three  dry  cells,  and  T  is  a  telephone.  The 


156 


WIRELESS   TELEGRAPHY. 


ends  of  the  wires  A  and  A'  are  smeared  at  the  gap  G  with 
a  minute  quantity  of  a  paste  which  the  inventor  has  named 
"goo."  By  means  of  the  adjusting  screws  F  F'  the  ends 
of  A  A'  are  first  brought  together  within  the  tube,  and 


Fig.  49. 

then  slowly  separated,  until  by  repeated  trials  the  amount 
of  space  which  is  best  for  clear  signals  has  been  attained. 

It  will  be  understood  that  the  "  goo  "  thus  bridges  the 
gap  between  the  electrodes.  Through  a  microscope  the 
paste  is  seen  to  lie  in  tiny  globules  which  just  touch  one 


WAVE-RESPONSIVE-DEVICES.  157 

another,  but  under  the  action  of  impinging  waves  these 
globules  decompose  and  decohere,  the  effect  being  to 
increase  the  electrical  resistance  of  the  closed  circuit, 
which,  as  in  Fig.  49,  contains  a  battery,  a  paste-filled  gap 
G,  and  a  telephone  receiver. 

Now  a  telephone  receiver  gives  forth  audible  sounds  in 
response  to  the  slightest  change  in  resistance,  whether 
diminished  or  augmented ;  and  thus,  whenever  a  long- 
wave effect  or  a  short-wave  effect  is  produced  at  the 
sending  end,  it  is  indicated  at  the  receiving  end  by  long 
or  short  buzzing  sounds  in  a  telephone  held  or  attached  to 
the  ear  of  an  operator. 

Ehret  System Reference  to  the  text   and  diagrams 

which  describe  the  system  of  Mr.  Ehret l  will  serve  to  ex- 
plain one  use  of  an  anti-coherer  in  connection  with  a  relay. 


MICRO-RADIOPHONES. 

Carbon  Powder  Wave-Detector  of  1897 There  is  rec- 
ord of  the  employment,  about  1897,  of  a  carbon  powder 
coherer  by  which  Professor  Jervis  Smith  of  Oxford  Uni- 
versity, England,  maintained  communication  over  more 
than  a  mile  of  space.  So  far  as  I  can  discover,  this  is  the 
earliest  specimen  of  a  type  that  is  now  known  as  the 
micro-radiophone  or  micro-radio-receiver. 

Popoff's  Micro-Radiophone  of  1900 — In  May,  1900, 
Professor  Popoff  of  Russia,  as  the  result  of  experimenta- 
tion, concluded  that  it  was  possible  to  eliminate  the 

1  See  Fig.  30,  Part  I.,  and  accompanying  description. 


WIRELESS   TELEGRAPHY. 


coherer  and  relay  by  substituting  for  both  either  a  micro- 
phonic  arrangement  of  steel  needles,  having  their  extremi- 
ties resting  upon  plates  of  carbon,  or  by  mixing  steel 
filings  and  carbon  powder. 

Shoemaker's   Steel  and  Carbon  Wave-Detector The 

steel  and  carbon  powder  type  of  Professor  Popoff  has  been 
the  subject  of  many  patented  inventions,  one  of  which,  by 
Mr.  Shoemaker  of  Philadelphia,  consists  of  a  number  of 
steel  balls  in  a  horizontal  line,  the  space  between  the  balls 
being  filled  with  carbon  powder. 

Shoemaker  and  Pickard  Needle  and  Carbon  Wave- 
Detector Another  invention  was  patented  in  the  United 

States,  in  August,  1902,  by  Messrs.  Shoemaker  and 
Pickard.  As  expressed  in  the  patent,  — 

"  It  comprises  a  wave-responsive-device  whose  essential  elements  are  of 
carbon  and  steel,  respectively.  A  wave-responsive-device  composed  of 

these  materials  has 
the  property  of  great 
delicacy  and  sensi- 
tiveness in  respond- 
ing to  electrical  ra- 
diations, and  has 
also  the  desirable 
property  of  regaining 
its  normal  condition  after  the  cessation  of  influence  of  electrical  waves. 

"  More  specifically,  our  invention  comprises  carbon  terminal  blocks,  in 
contact  with  which  are  steel  or  iron  needles,  which  serve  to  close  the 
circuit  from  one  carbon  block  to  the  other.  As  an  alternative,  however,  it 
is  to  be  understood  that  the  terminal  blocks  may  be  of  steel,  and  that  car- 
bon filaments  or  rods  may  contact  with  them  to  close  the  circuit. 

«'  The  wave-responsive-device  herein  described  is  connected  with  any  of 
the  wireless  signaling  systems  in  the  same  relation  as  the  numerous  types 
of  wave-responsive-devices  heretofore  used." 

In  Fig.  50,  1 6  is  a  glass  tube  or  any  suitable  envelope,  on  the  right-hand 


WAVE-RESPONSIVE-DEVICES.  1 59 

end  of  which  is  a  metallic  cap  17,  through  which  is  tapped  the  screw  18, 
which  at  its  left-hand  end  screws  into  the  central  insulating  portion  19, 
thereby  clamping  between  said  portion  19  and  a  brass  nut  20  the  carbon 
disk  21. 

22  is  a  metallic  cap  upon  the  left-hand  end  of  the  tube  16,  and  from 
which  extends  into  the  tube  rod  23,  secured  in  said  cap  22,  and  also  into 
insulating  block  19,  thereby  clamping  between  said  block  19  and  a  nut  24 
the  carbon  disk  25. 

26  and  27  are  disks  of  insulating  material,  which  serve  to  center  and 
steady  the  device  in  tube  16.  It  is  to  be  noticed  that  the  disks  of  carbon 
21  and  25  are  slightly  smaller  in  diameter  than  the  tube  16 
for  the  purpose  of  preventing  their  contact  with  said  tube 
during  assemblage,  inasmuch  as  such  contact  might  serve 
to  destroy  the  disks,  due  to  the  fact  that  they  are  thin  and 
fragile.  On  to  the  left  end  of  the  cap  22  screws  a  cylin- 
drical  piece  28,  forming  between  28  and  22  a  cavity  29, 
designed  to  receive  calcium  chlorid  or  other  desiccating  material  for  keep- 
ing the  air  or  other  gas  within  the  tube  16  perfectly  dry.  Communication 
between  29  and  the  interior  of  tube  16  is  obtained  by  numerous  holes,  as 
30.  On  the  piece  28  is  the  binding-post  31,  serving 

25- fy_l_ "21    as  one  terminal  of  the  device,  while  cap  17  or  screw 

1 8  serves  as  the  other  terminal. 

Fig.  51  represents  a  plan  view  of  one  of  the  car- 
34          •         bon  disks  —  as,  for  example,  25  —  which  shows  sym- 
Fig.  52.  metrically-arranged  small  holes    32,  while  the  inner 

large  hole  33  permits  the  passage  of  the  rods  i8or  23. 
In   Fig.   52  are  shown  the   two   carbon  disks  21  and  25,  supporting 
between  them  the  needles  34. 


This  Shoemaker  and  Pickard  organization  is  an  elabora- 
tion of  the  Popoff  microphonic  receiver  of  1900,  and  is 
typical  of  its  class. 

Fessenden.      Silver   Ring   and    Knife-edge    Contact.  — 

Fig.  5  3  illustrates  a  radio-receiver  designed  by  the  United 
States  Government  expert,  Mr.  Fessenden.  7  repre- 
sents a  coil  of  wire  which  is  a  magnetic  field  for  an  arma- 
ture 8,  the  latter  being  made  preferably  in  the  form  of  a 


i6o 


WIRELESS   TELEGRAPHY. 


silver  ring.  Ring  8  is  balanced  upon  two  knife  edges  13 
and  13',  one  of  which,  as  13,  is  formed  of  a  good  electrical 
conductor,  for  example,  silver ;  and  the  other,  1 3',  is  out  of 
circuit.  A  carbon  block  14  is  so  arranged  that  the  por- 
tion between  it  and  knife  edge  1 3  of  the  ring  8  forms  part 
of  an  electrical  circuit.  Waves  passing  from  the  gate  6  to 
the  earth  and  energizing  field  coil  7  will  cause  the  ring  8 
to  press  upon  the  carbon  block  14,  thereby  increasing  the 
conductivity  of  the  contact  between  8  and  14. 

"  When  using  a  telephone-receiver  as  a  recording  instru- 
ment, the  generator  1 5  is  preferably  of  a  character  capable 
of  producing  an 
alternating  cur- 
rent, as  such  cur- 
rent causes  a 
constant  vibra- 
tion of  the  dia- 
phragm, the 
vibrations  in- 
creasing in  in- 
tensity with  an 
increased  flow 
of  current  in 
the  circuit.  This  increase  in  intensity  of  action  with  in- 
creased flow  of  current  is  characteristic  of  this  form  of 
receiver.  In  this  it  is  sharply  differentiated  from  such 
devices  as  the  coherer,  which  either  give  a  strong  indica- 
tion or  do  not  give  any.  This  characteristic  is  advanta- 
geous in  that  if  the  signal  sent  —  say  a  dot  —  be  too  weak 
to  give  an  action  of  the  full  intensity,  it  may  still  in  most 
cases  be  read  and  not  missed  entirely,  which  is  of  value  in 
sending  code-messages." 


15 


Fig.  53- 


WAVE-RESPONSIVE-DEVICES. 


161 


The  Code-Message  Trouble.  —  The  above  allusion  to 
"code-messages"  was  probably  first  suggested  by  a 
declaration  of  the  ocean  cable  companies  that  the  Marconi 
Company  could  not  transmit  code-messages, — an  idea  now 
prevalent  among  inventors  competing  with  the  Marconi 
Company.  Why  the  transmission  of  dots  should  not  be 
necessary  in  ordinary  messages  has  not  been  made  clear ; 
nor  why  there  should  be  obstacles  to  the  passage  of  code- 
messages  which  are  sent  by  telegraphic  signals  exactly 
like  other  messages. 

Mr.  Fessenden's  description  of  Fig.  53  includes  the 
alternate  use  of  a  telegraphic  sounder  as  a  recording  in- 
strument in  place  of  the  telephone  (i 6)  shown;  but  it  is 
hardly  possible  that  a  sounder  in  such  position  can  have 
been  successfully  employed  in  practice. 

Marconi's  Opinion  of  Non-Tapping  Coherers.  —  In  a 
paper  read  before  the  Royal  Institution  of  London  in 


L/ 


CONNECTING 


V 
MERCURY 


V 


Fig.  54. 


June,  1902,  Signer  Marconi  says  of  non-tapping  coherers, 
that  they  are  not  sufficiently  reliable  for  commercial  work ; 
that  under  the  influence  of  strong  waves  or  of  atmospheric 
discharges  they  cohere  permanently ;  and  that  there  is  an 
unpleasant  tendency  to  suspend  action  in  the  middle  of  a 
telegram  ;  moreover,  that  as  their  resistance  is  continually 
varying,  it  is  difficult  to  syntonize  the  circuits  of  which 
they  form  a  part. 


162 


WIRELESS   TELEGRAPHY. 


Italian  Navy  Radio-Receiver. — The  radio-receiver  adopted 
by  the  Italian  navy,  a  result  of  the  combined  efforts  of  its 
experts,  is  a  composite  of  the  coherer  and  the  microphone 
receiver.  It  is  used  in  connection  with  a  circuit  syntonized 

in  the  usual  way  by  capa- 
city and  self-induction. 
The  marked  illustration, 
Fig.  54,  seems  sufficiently 
to  describe  it. 


MAGNETIC-RADIO- 
RECEIVERS. 

In  the  class  of  magnetic- 
radio-receivers  Mr.  Fes- 
sen  den  has  evolved  three 
distinct  types  and  Mr. 
Marconi  one. 

A  Fessenden  Magneto- 
Receiver Fig.  55  is  an 

illustration  of  one  of  Mr. 
Fessenden's      magneto-re- 
ceivers, in  which  7  and   7 
represent    field   coils    con- 
nected     respectively      to 
wave-gate  6  and  to  earth. 
8   is   an   armature  so  sus- 
pended that  the  reaction  of  the  current  induced  in  8  when- 
ever the  coils  7  are  energized  will  cause  8  to  move.     Such 
movement  may   be  made  observable    by    reflection    of   a 


WAVE-RESPONSIVE-DEVICES. 


I63 


12 


beam  of  light  from  the  mirror  9 
upon  a  scale.  The  slight  move- 
ment of  the  mirror  is  seen  in  the 
larger  movement  of  the  spot. 

Another  of  Mr.  Fessenden's 
devices  is  shown  in  Fig.  56,  in 
which  10  is  the  wave-gate  of  a  re- 
ceiving station  ;  1 2  is  a  fine  steel 
wire  held  under  tension  between 
the  poles  of  magnet  13;  14  is 

a  contact  normally  disconnected  from  wire  12  by  the  inter- 
action of  currents. 


Fig.  56. 


-10 


A  Second  Magneto-Receiver  by  Fessenden.  —  Fig.  57  is 
a  diagrammatic  representation  from  Mr.  Fes- 
senden's patent,  No.  706,747,  in  which  10  is 
the  antenna,  1 1  a  coil  having  one  terminal  con- 
nected to  the  antenna  10,  and  the  other  ter- 
minal grounded.  A  telephone  diaphragm  12, 
adapted  to  vibrate  in  unison  with  changes  of 
current  produced  by  waves  radiated  from  the 
12  sending  station,  is  suitably  supported  in  oper- 
ative relation  to  the  coil  1 1  ;  and  the  apparatus 
at  the  receiving  station  is  tuned  in  harmony 
with  the  emitter  of  the  sending  station. 

Marconi's    Hysteresis    Detector. — At     this 
writing  a  description  of  the  new  Marconi   re- 
ceiver has    been  published,  but  no  authorized 
illustration    of    it    has  been  printed.      In    Fig. 
Fig.  57.        58  an  attempt  is  made  to  follow  in  diagram  the 


164  WIRELESS   TELEGRAPHY. 

Marconi  text.  The  discovery  upon  which  this  new  appa- 
ratus is  based  is  the  fact  that  hysteresis  is  decreased  by 
the  action  of  Hertzian  waves. 

Hysteresis  Defined.  —  Whenever  iron  is  subjected  to 
changes  in  magnetic  strength  or  magnetic  polarity  it  gen- 
erates and  radiates  heat.  This  phenomenon  is  called 
"  hysteresis,"  and  the  amount  of  heat  dissipated  as  loss  by 
reason  of  such  changes  is  known  as  "  hysteresis  loss." 

Changes  of  Polarity  in  Iron.  How  Produced.  —  Differ- 
ences in  polarity  may  occur  from  movements  of  the  iron 
itself,  as  when  the  armature  of  a  dynamo  revolves ;  or  from 
the  movements  of  a  magnet,  as  when  a  dynamo  field  is 
caused  to  move  about  a  stationary  armature ;  or  from 
changes  in  the  exciting  cause,  as  when  an  alternating  cur- 
rent is  made  to  pulsate  through  a  transformer. 

Quantitative  Effects.  —  Quantitatively,  hysteresis  effect 
depends  upon  the  amount  of  iron  under  influence  ;  upon 
the  quality  of  the  metal,  wrought-iron  or  steel  being  more 
affected  than  soft  iron  ;  upon  the  density  of  magnetism  in 
the  iron  ;  and  upon  the  rapidity  of  the  movements  which 
cause  the  changes  in  magnetic  direction  or  magnetic 
power. 

Theory.  —  Theoretically,  it  has  been  explained  that  heat 
is  generated  by  friction  as  the  molecules  of  iron  in  mag- 
netic action  turn  over  and  thus  rub  against  one  another. 

Description  of  Marconi  Magnetic  Detector.  —  Referring 
to  Fig.  58,  upon  a  core  C,  which  consists  of  fine  iron  wires, 


WAVE-RESPONSIVE-DEVICES. 


I65 


are  wound  one  or  two  layers  B  of  thin  insulated  copper 
wires.  Over  this  winding  B,  is  an  insulating  coating  G ; 
around  the  insu- 
lating envelope 
a  bobbin  F  F ; 
and  upon  the 
bobbin  a  wind- 
ing of  small  in- 
sulated wires, 
D.  The  ends  of  C 
the  winding  B 
are  connected 
respectively  to 
the  antenna  A 
and  the  earth  at 
E  ;  and  the  ends 
of  the  winding  Fig-  s8- 

D  to  the  telephone  T.  One  face  of  the  core  C  is  pre- 
sented to,  and  magnetized  by,  the  magnet  M.  Upon  being 
revolved  by  clock  work,  W,  the  movements  of  M  cause 
constant  reversals  in  the  polarity  of  core  C,  and  conse- 
quently a  certain  hysteresis  effect  is  produced.  Whenever 
this  effect  is  modified  by  the  influence  of  Hertzian  waves, 
an  audible  record  of  such  waves  is  made  on  the  tele- 
phone receiver. 

Practical  Results  From  Marconi  Magnetic   Detector. — 

For  some  time  the  form  of  detector  just  described  has 
been  in  successful  operation  over  a  distance  of  one  hun- 
dred and  nine  miles  of  sea  surface,  and  forty-three  miles  of 
high  land,  a  total  of  one  hundred  and  fifty-two  miles. 
Marconi  seems  to  think  it  is  more  sensitive  and  more  re- 


1 66  WIRELESS   TELEGRAPHY. 

liable  than  a  filings  coherer.  Less  electromotive  force 
than  with  a  coherer  is  required  at  the  sending  station  ;  its 
resistance  is  uniform  ;  and  many  of  the  precautions  and 
delicate  adjustments  necessary  where  a  coherer  is  used 
may  be  neglected  with  the  hysteresis  detector. 

^f":  ~~ ~~-"~~  • 

Coherer  Organization  Needed  to  Call.  —  So  far,  however, 

in  order  to  "call,"  it  has  been  necessary  to  use  with  the 
new  receiver,  a  coherer,  relay,  and  bell.  The  only  suc- 
cessful indicator  of  signals  in  connection  with  it  is  a  tele- 
phone receiver.  If,  as  the  tests  seem  to  indicate,  a  visual 
record  can  be  made  and  retained,  Mr.  Marconi  thinks 
it  will  be  possible  to  transmit  several  hundred  words  per 
minute. 

A  Wave-Responsive-Device  by  Fessenden.  —  It  may  be 

assumed  that  the  result  of  Mr.  Fessenden' s  labors  for  the 
United  States  Government,  so  far  as  wave-responsive- 
devices  are  concerned,  is  the  subject  of  his  patent  No. 
706,744,  for  which  application  was  made  on  June  6,  1902, 
from  the  laboratory  at  Manteo,  North  Carolina.  In  patent 
No,  706,745,  the  inventor  claims  that  with  the  device  so 
fully  described  in  706,744  "  messages  at  the  rate  of  thirty 
words  per  minute  were  sent  and  received  over  a  distance  of 
fifty  miles,  from  Cape  Hatteras  to  Roanoke  Island,  using 
at  the  sending  end  a  spark  only  one  thirty-second  of  an 
inch  long."  This  form  of  radio-receiver  from  the  Fessenden 
patents  cannot  be  included  in  any  of  the  four  classifications 
just  discussed.  The  patentee  himself  describes  it  as  "a 
current-actuated  wave-responsive-device  consisting  of  a  con- 
ductor having  a  small  heat  capacity  and  arranged  in  a 


WAVE-RESPONSIVE-DEVICES. 


I67 


Description  of  Fessenden's  Heat-Receiver.  —  Fig.  59  is 
a  diagrammatic  illustration- 
reproduced  from  Mr.  Fes- 
senden's patent  706,744,  in 
which  17  is  a  glass  bulb. 
Into  it  are  sealed  two  lead- 
ing-in  conductors  of  plati- 
num wire,  1 6  16.  18  is  a 
silver  shell  having  at  its 
top  a  glass  brace  19,  hold- 
ing the  wires  16  16.  The 
platinum  wires,  except  at 
the  tip  14,  are  coated  with 
silver.  The  tip  14  which 
is  left  uncoated  is  a  minute 
part,  being  but  a  few  hun- 
dred thousandths  of  an  inch 
in  length.  Having  small 
volume  and  capacity,  the 
loop  14  is  capable  of  being 
quickly  raised  in  tempera- 
ture an  appreciable  amount, 
and  it  is  equally  capable 
of  quick  cooling,  thus  pro- 
ducing rapid  changes  in 
electrical  resistance. 


Fig.  59. 


168  WIRELESS    TELEGRAPHY. 


WAVE-GATES. 

Marconi's  Early  Experiments  in  England In  England, 

about  August,  1896,  Mr.  Marconi  transmitted  signals  over- 
land a  distance  of  two  miles.  No  ground  connection 
either  at  the  sending  or  receiving  stations  was  used. 

Adoption  of  High  Wire  and  Earth  Terminal The  next 

steps  in  the  Marconi  system  were  the  adoption  of  an  ele- 
vated terminal  and  an  earth  terminal.  On  May  n,  1897, 
Marconi,  who  was  conducting  experiments  at  Lavernock 
Point,  England,  failed  of  results.  His  receiving  apparatus 
was  set  upon  a  cliff  sixty  feet  above  the  level  of  the  sea. 
Here  was  erected  a  pole  ninety  feet  in  height  capped  with 
a  cylinder  of  zinc  six  feet  long  and  three  feet  in  diam- 
eter. An  insulated  copper  wire  was  fastened  to  the  cap, 
led  down  the  pole,  and  from  it  made  connection  to  one  end 
of  the  coherer.  The  other  end  of  the  coherer  was  con- 
nected to  a  wire  which  was  dropped  down  the  cliff  and 
dipped  in  the  sea. 

Communication  Established  by  Better  Earth  and  Longer 
Wave-Gate.  —  Both  on  that  day  and  on  the  following,  at- 
tempts at  transmission  were  unsuccessful;  but  on  May  13, 
the  coherer  and  other  receiving  instruments  having  been 
carried  to  the  bottom  of  the  cliff,  communication  was  at 
once  established.  The  antenna  by  the  change  to  the 
bottom  of  the  cliff  had  been  lengthened  to  one  hundred 
and  fifty  feet.  The  earth  connection  had  been  strength- 
ened by  the  elimination  of  such  resistance  as  was  furnished 
by  sixty  feet  of  wire. 


WAVE-GATES.  169 

Lodge's  Early  "  Collecting  Wire."—  In  Dr.  Lodge's  first 
patent,  filed  December  20,  1897,  his  wave-gate  served  for 
the  reception  of  impulses,  and  was  called  by  the  inventor  a 
"  collecting  wire."  Presumably  it  was  but  a  few  feet  in 
length.  Quoting  from  that  patent :  "  In  some  cases  I  find 
that  any  bare  wire,  or  a  connection  to  earth  direct  or 
through  the  system  of  gas  or  water  pipes,  will  serve  suffi- 
ciently well  as  a  collector  or  as  an  assistance  to  the  insu- 
lated collector." 

Lodge  Emitter.  —  Lodge  devised  a  form  of  emitter l  in 
which  electricity  was  "supplied  to  a  single  conductor  a 
suddenly  or  disruptively  by  a  couple  of  positive  and  nega- 
tive sparks  from  knobs  b  and  c.  A  partial  metallic  inclos- 
ure  d  could  be  used  to  diminish  waves  in  an  undesired 
direction.  There  seems  to  have  been  no  extension  into 
space  from  the  sphere  a  ;  nor  any  switching  communication 
between  the  sending  and  receiving  sides  of  his  apparatus. 

A  Supposed  Law.  —  When  virtue  was  found  to  exist  in 
an  elevated  wire,  Mr.  Marconi  made  a  number  of  experi- 
ments from  which  he  deduced  the  law  that  the  distance 
over  which  signals  could  be  transmitted  varied  as  the 
square  of  the  height  of  the  vertical  conductors. 

Lodge's  Cones.  —  It  was  soon  found,  however,  that  no 
such  law  existed,  and  the  attention  of  experts  in  wireless 
telegraphy  was  next  given  to  devising  wave-gates  lower  in 
height  but  greater  in  surface  area.  Dr.  Lodge,  in  his 
United  States  patent  filed  February  i,  1898,  says:  "I 
prefer  for  the  purpose  of  combining  low  resistance  with 

1  Lodge  patent,  Appendix  II. 


1 70  WIRELESS    TELEGRAPHY. 

great  electrostatic  capacity,  cones,  or  triangles,  or  other 
such  diverging  surfaces,  with  the  vertices  adjoining  and 
their  larger  areas  spreading  out  into  space."  Manifestly 
such  a  construction  as  is  shown  in  Fig.  25,  Part  I.,  would 
be  especially  weak  to  resist  wind  pressure,  and  so  the 
inventor  recommended  a  modification  in  the  form  of  a 
roof,  as  illustrated  in  Fig.  21,  Part  I. 

Marconi's  Thick  Copper  Cable. —  In  a  patent  filed  Janu- 
ary 5,  1899,  Marconi  describes  two  wave-gates.  The  first 
was  an  insulated  cable  consisting  of  seven  strands,  each 
strand  made  of  seven  copper  wires,  each  one  millimeter  in 
diameter,  thus  making  the  total  diameter  of  the  cable,  the 
number  of  wires  being  forty-nine,  nine  millimeters,  or 
thirty-six  hundredths  of  an  inch.  This  copper  cable  was 
suspended  vertically  from  a  height  of  one  hundred  and 
thirty  feet. 

Marconi's  Iron  Netting.  — The  second  was  a  galvanized 
wire  netting  two  feet  broad  and  one  hundred  and  thirty 
feet  long,  the  top  of  the  netting  being  about  one  hundred 
and  ten  feet  from  the  ground. 

Marconi's  Observations  on  Wave-Gates  in  May,  1901. — 

In  a  paper  before  the  Royal  Society  of  Arts  of  London, 
May  15,  1901,  Signor  Marconi  said  :  "  The  original  elevated 
straight  wire  which  was  used  as  a  transmitter  was  a  very 
good  radiator  of  electric  waves  ;  but  its  electric  oscillations 
died  away  with  great  rapidity,  though  very  powerful  while 
they  lasted.  If  a  radiator  be  used  giving  off  much  less 
energy  at  each  vibration,  but  emitting  a  series  of  waves 


WAVE-GATES. 


171 


over  an  extended  period,  then  it  will  only  affect  a  resonator 
tuned  to  that  particular  frequency.  It  will  take  some 
time,  measured  in  thousandths  of  a  second,  for  the  radi- 
ator to  set  up  a  swinging  electric  force  in  the  receiver 
sufficient  to  break  down  the  insulation  of  the  coherer." 

He  further  observed,  in  the  same  paper,  that  "  early  in 
1900  the  vertical  wire  was  replaced  by  the  zinc  cylinder 
oscillators."  The  zinc  cylinders  are  illustrated  in  Part  II. 
as  Fig.  37,  and  in  the  text  accompanying  that  figure  are 
described  at  length. 

Fessenden's  Wave-Gates  of  Low  Resistance  and  Large 

Capacity In    May,    1901,    Mr.    Fessenden: 

who  had  evidently  been  working  along  the 
same  lines  as  Marconi,  filed  two  patent  appli- 
cations whose  subject  matter  chiefly  concerned 
radiating  conductors  of  low  resistance  and 
large  capacity.  Two  of  these  are  shown  in 
Figs.  60  and  61.  The  inventor  describes 
them  as  "  sending  conductors  for  electromag- 
netic waves,"  and  says  that  they  have  a  large 
capacity  distributed  with  substantial  uniform- 
ity over  the  radiating  portion,  and  that  this 
capacity  is  so  adjusted  that  the  waves  radiated 
from  the  conductors  have  a  low  frequency. 
These  conductors,  it  will  be  observed,  differ 
from  the  Lodge  cones  in  that,  except  for  the 
enlargement  in  Fig.  61,  they  are  uniform  in 
figure. 

Mr.  Fessenden  says  it  has  been  held  that  the  capacity 
of  the  upper  portion  of  a  conductor  of  uniform  cross  sec- 
tion is  much  lower  than  that  of  the  middle  or  lower  por- 


Fig.  60. 


172 


WIRELESS    TELEGRAPHY. 


tion ;  but  that  by  actual  measurements  he  has  found  this 
not  to  be  the  case,  the  upper  portions  having  practically 
the  same  capacity  as  the  lower.  Further,  he 
says,  that  when  far  from  the  ground  the  capa- 
city of  a  conductor  with  respect  to  that  ground 
is  dependent  not  upon  its  distance  from  the 
earth,  but  upon  its  size  and  shape.  Of  the  en- 
largement (17)  in  the  middle  of  the  sending 
conductor  shown  in  Fig.  61,  the  inventor  says : 


"  The  effect  of  locally  increasing  the  superficial  area  of 
the  sending-conductor,  or  of  locally  increasing  the  capacity 
Fig.  61.  ky  any  other  suitable  means,  is  to  produce  two  or  more 
sets  of  waves  of  different  periodicities,  the  periodicity  of  the  first  being 
dependent  upon  the  electrical  constants  of  the  sending-conductor  as  whole, 
and  the  periodicity  of  the  other  depending  upon  the  position  and  amount 
of  localized  increase  of  capacity,  in  the  same  wyay  as  by  attaching  a  weight 
or  spring  to  a  piano  wire  between  its  extremities  additional  vibrations  in 
the  wire  are  created." 


Fessenden's  Wave-Gates  of  High  Specific  Inductive  Capa- 
city.—  Figs.  62  and  63  are  from  the  Fessenden  patent 
706,739.  The  first  is  a  sectional  elevation,  and  the  second 


Fig.  62. 


Fig.  63. 


a  plan  of  a  sending  conductor  similar  in  configuration  to 
that  shown  in  Fig.   61,  but  now  surrounded  by  a  coil  of 


WAVE-GATES.  173 

wire,  between  the  turns  of  which  is  supplied  an  insulating 
medium  of  high  specific  inductive  capacity.  "  By  this 
means,"  the  patent  declares,  "it  is  possible  to  increase  the 
capacity  of  the  conductor  without  altering  its  height,  and 
yet  without  altering  the  relation  between  the  wave  length 
and  the  medium  and  the  length  of  the  conductor.  In  other 
words,  to  obtain  the  same  effect  as  is  produced  in  air  by 
increasing  the  height  of  the  conductor  "  ;  or,  again,  "that 
all  the  functions  or  desirable  results  incident  to  the  employ- 
ment of  a  long  high  conductor  can  be  attained  by  a  rela- 
tively short  low  conductor." 

In  Figs.  62  and  63  reference  number  I  indicates  the 
radiating  portion  proper ;  2  may  consist  of  a  coil  of  insu- 
lated iron  wires  of  No.  40  Brown  &  Sharpe  gauge.  The 
wires  in  the  coil  are  maintained  under  tension,  the  turns 
being  spaced  a  distance  apart  approximately  one-fourth  the 
diameter  of  the  wire.  The  spaces  between  the  wires  2 
may  be  filled  with  an  insulating  material  of  high  specific 
inductive  capacity,1  such  as  rubber,  indicated  by  a  black 
mass  in  the  figure  ;  3  is  a  reflecting  plate  formed  of  metal 
and  arranged  on  the  side  of  the  conductor  opposite  that 
facing  the  direction  in  which  the  waves  are  to  travel ; 
4  4  are  spark  knobs ;  7  is  an  enlargement  for  a  purpose 
similar  to  reference  number  17  of  Fig.  61.  Of  7  the 
inventor  says,  it  may  be  a  band  of  conducting  material, 
and  that  such  a  construction  affords  means  for  adjust- 
ing the  capacity  by  adding  or  removing  bands,  or  by 
changing  their  position  along  the  conductor.  The  main 
advantage,  and  a  matter  of  especial  necessity  to  the  Fes- 
senden  system,  is  that  this  device  enables  the  operator  to 
obtain  long  waves  from  a  short  conductor,  thereby  avoid- 
ing the  expense  involved  in  the  erection  of  high  masts. 

1  See  p.  183. 


174 


WIRELESS   TELEGRAPHY. 


Fessenden's  Wave-Chute Another  Fessenden  inven- 
tion is  for  a  "wave-chute,"  called  also  an  "artificial 
ground."  Of  this  device  Fig.  64  is  an  elevation  and  Fig. 
65  a  plan.  In  those  illustrations  reference  numbers  2 


13 


Fig.  64. 

are  longitudinal  wires  in  the  wave-chute ;  and  3,  trans- 
verse wires  connecting  together  wires  2  ;  1 1  is  a  metallic 
guy  rope  or  chain  for  supporting  the  mast.  In  one  of 
his  descriptions  of  the  wave-chute  the  inventor  says : 

INVENTOR'S  DESCRIPTION  OF  WAVE-CHUTE.  —  "I  have  found  that  it 
is  essential  for  the  proper  sending  and  receipt  of  these  waves  that  the  sur- 
face over  which  they  are  to  travel  should  be  highly  conducting,  more  espe- 


Fig.  65. 

daily  in  the  neighborhood  of  the  point  where  the  waves  are  generated.  I 
have  found  that  this  highly-conducting  portion  of  the  surface  should  pref- 
erably extend  to  at  least  a  distance  from  the  origin  equal  to  a  quarter  wave 
length  of  the  wave  in  air,  and  in  the  direction  toward  the  station  or  sta- 
tions to  which  it  is  desired  to  send  the  waves.  Where  the  sending-station 
is  in  a  city  or  similar  place  where  the  waves  may  be  cut  off  by  high  build- 
ings or  high  trees,  this  highly-conducting  path  should  be  extended  still 


*/ 

WAVE-GATES,  1/5 

farther,  until  it  passes  beyond  the  limits  of  the  obstacle,  and  there  the 
highly-conducting  portion,  which  may  be  in  the  form  of  a  strip  of  metal  or 
other  conductor,  or  of  a  number  of  wires,  is  connected  to  ground." 

and,  further,  that  "  on  rocky  shores,"  as  an  instance,  "  salt 
spray  sometimes  dashes,  rendering  the  ground  surface  near 
the  station  a  conducting  one  which  was  previously  an  insu- 
lating one ;  and  in  such  case  an  artificial  ground  makes  the 
conditions  constant  in  all  weathers." 

Preventing  Absorption  of  Waves  into  Iron  or  Steel  Guys. 

—  "  That  it  is  preferable  in  such  places  to  employ  iron 
chains  or  iron  wire  ropes,  and  that  such  iron  or  steel  guys 
would  in  general  absorb  waves  rapidly,"  therefore  he  coats 
them  and  the  mast  with  a  non-magnetic  film,  such  as  zinc 
or  lead,  thus  rendering  their  resistance  to  the  currents  pro- 
duced by  electromagnetic  waves  of  the  frequency  used  so 
low  that  there  is  little  absorption.  It  is  desirable  that  the 
guys  be  insulated  from  the  ground,  and  "  in  order  to  ren- 
der it  certain  that  the  natural  period  of  the  mast  and  guys 
is  different  from  that  of  the  electromagnetic  waves,  said 
mast  and  guys  may  be  wrapped  or  encircled  with  one  or 
more  coils  or  turns  (13)  of  iron  strips,  or  wire,  preferably 
insulated,  thus  increasing  the  inductance  and  natural 
period  of  the  mast  and  guys,  and  permitting  the  employ- 
ment of  conducting  material  —  e.g.,  iron  or  steel  —  in  the 
mast  and  guys.  As  shown  in  Fig.  64,  the  coils  or  turns 
may  be  either  formed  locally,  — i.e.,  extending  a  short  dis- 
tance along  the  mast  or  guys,  —  or  such  coils  or  turns 
may  extend  continuously  along  such  parts. 

"  While  the  coating  of  the  mast  and  guys  with  non-mag- 
netic material  need  not  necessarily  be  used  with  the  coils 
or  turns,  it  is  preferred  in  most  cases  to  both  coat  the 
mast  and  guys  with  non-magnetic  material  and  also  to 


WIRELESS   TELEGRAPHY. 


employ  the  coils  or  turns  of  magnetic  wire  or  strips,  which 
may  be  formed  of  nickel  or  other  magnetic  material.  No. 
40  Brown  &  Sharpe  gauge  of  wire  is  a  size  suitable  for  the 
purpose." 


Probable  Law  or  Wave-Propagation  Through  Space.  - 

It  seems  natural  and  probable  that  the  dissipation  of 
energy  in  wave-propagation  through  space  follows  laws 
analogous  to  those  that  govern  the  conduction  of  electrical 
currents  along  wires,  that  the  amount  of  loss  is  inversely 
proportional  to  the  cross-sectional  area  of  the  conducting 

medium  and  to  the 
square  of  the  applied 
pressure.  If  etheric 
waves  are  radiated  in 
straight  lines,  then  the 
cross-sectional  area  of  a 
wireless  conductor  is  the 
product  of  the  height  and 
the  mean  horizontal  peri- 
phery of  the  wave-gate. 
It  is  also  true  that  the 
amount  of  energy  which 
may  be  transferred  from 
the  surface  of  the  send- 
ing conductor  to  the 
other  is  modified  by  the  resistance  to  vibrations  of  the 
carrier  which  conveys  those  vibrations  from  the  initial 
source  of  wave  generation  to  the  emitting  surfaces. 

The  Marconi  Wave-Gates  at  Poldhu  and  Glac<§  Bay.  - 

Figs.  66,  67,  and  68  are,  respectively,  illustrations  of  the 


Fig.  66. 


WAVE-GATES. 


177 


Marconi  Company's  wave-gates  at  Poldhu,  England,  and  at 
Glace  Bay,  Cape  Breton.     Fig.  68  carries  out  the  idea  of 


Fig.  67. 

Professor  Lodge,  referred  to  at  some  length  in  Part  II., 
and  also  mentioned  in  the  present  part  in  connection  with 
Lodge's  wave-gate. 


Fig.  68. 


Cape  Breton  is  an  island  and  politically  a  part  of  the  prov- 
ince of  Nova  Scotia.     It  is  twelve  miles  from  Sydney,  and 


178  WIRELESS   TELEGRAPHY. 

separated  from  the  main  land  by  the  Strait  of  Canso. 
Each  of  the  four  towers,  shown  in  the  Glace  Bay  picture, 
are  two  hundred  and  fifteen  feet  high.  They  form  a 
square,  each  side  of  which  is  two  hundred  feet  in  length. 
Between  the  eastern  towers  and  the  sea  the  ground  is 
absolutely  bare  of  soil.  The  structures  are  composed  of 
strong  steel  timbers  bolted  together  and  firmly  anchored 
in  foundations  of  cement  concrete.  At  different  heights 
depend  from  the  towers  hundreds  of  steel  guys  (not  shown 
in  the  picture)  are  secured  to  the  rocky  surface  of  the 
ledge  from  a  few  feet  to  fifty  yards  from  their  respective 
bases. 


SHIELDS. 


179 


SHIELDS. 

A  device  peculiar  to  Wireless  Telegraphy  is  the  metal 
shield  used  to  protect  the  coherer  from  the  strong  waves 
of  a  transmitter  in  close  proximity  at  the  same  station. 

Fig.  69  shows  one  of  Dr.  Lodge's  devices,  which  he  thus 
describes  : 


COHERER  SENSITIVE  TO  LOCAL  AS  WELL  AS  DISTANT  OSCILLATIONS. 
—  "  A  coherer  is  sensitive  not  only  to  the  desired  impulse  arriving  from  a 


h 


CIF 


Fig.  69. 

distance  and  conveyed  to  it  by  the  collectors,  but  it  is  also  liable  to  respond 
to  any  local  sparks  or  electric  surgings  in  its  neighborhood,  especially  to 
oscillations  in  an  adjacent  emitter.  It  may  be  protected  from  all  these  by 
complete  inclosure  in  a  flawless  metallic  box." 

PROTECTION  BY  METALLIC  COVERING.  —  "  For  the  purpose  of  protect- 
ing the  coherer  from  undesired  disturbance,  therefore,  I  inclose  it  (some- 
times with  all  coils,  wires,  batteries,  and  the  like  connected  to  it)  in  a 
metallic  covering  or  case,  as  shown  in  Fig.  69,  leaving  only  one  or 


180  WIRELESS   TELEGRAPHY. 

more  round  holes  or  short  tubes  w  for  the  collector  terminal  or  terminals 
to  enter  by,  and  for  vision  or  other  needful  purpose  requiring  an  aperture, 
for  through  round  holes  of  moderate  size  large  electric  waves  do  not 
readily  pass,  whereas  through  chinks  or  long  slits,  no  matter  how  infinitely 
narrow,'  they  can  pass  with  ease.  They  likewise  pass  in  by  means  of  any 
insulated  wire  which  enters  the  box  ;  but  through  any  wire  wrhich  is  thor- 
oughly joined  to  the  metal  wall  of  the  box  where  it  enters  the  waves  cannot 
pass." 

DESCRIPTION  OF  FIG.  69.  —  "In  the  particular  arrangement  shown 
in  Fig.  69  a  single  terminal  h  is  employed  which  is  insulated  from  the  cas- 
ing by  tube  w,  and  is  connected  to  one  terminal  only  of  the  coherer.  This 
construction  is  effective  and  desirable  in  certain  cases,  and  it  is  found  that 
the  Hertzian  waves  pass  in  readily  through  the  single  wire.  Hence  it  is 
not  absolutely  necessary  to  remove  the  terminal  h  from  its  aperture  when 
it  is  not  being  used  for  the  purpose  of  establishing  communication  and 
enabling  waves  from  the  collector  to  enter  the  box  and  reach  the  coherer. 

"  The  only  part  of  the  coherer  or  detector  portion  outside  the  box  is 
the  index  or  needle  mirror  z  of  the  telegraphic  receiving  instrument  em- 
ployed, which  is  acted  upon  and  deflected  by  its  coil  g  inside  acting 
magnetically  through  the  metal  wall. 

"  When  the  plan  of  withdrawing  the  terminals  of  the  box  is  adopted,  it 
is  sufficient  to  put  the  coherer  above  mentioned  alone  in  the  box." 

Marconi's  Shield.  —  Marconi's  organization  for  shielding 
his  coherer  is  illustrated  in  Fig.  70. 
His  own  description  is  as  follows  : 

"  When  both  instruments  are  employed  at  the  same  station,  it  is  found 
that  the  sensitive  tube  or  sensitive  imperfect  contact  is  liable  to  injury  by 
its  close  proximity  to  the  sparking  appliance.  In  order  to  obviate  this 
objection,  I  inclose  the  receiver  containing  the  sensitive  tube  or  sensitive 
imperfect  contact  in  a  box  of  metal  having  only  a  small  opening  into  it, 
and  I  employ  the  same  conductor  and  earth-plate  for  both  instruments. 
The  earth-plate  is  permanently  connected  to  one  terminal  of  the  sparking 
appliance  and  to  the  outside  of  the  box.  The  insulated  conductor  can  be 
connected  by  a  plug  either  to  the  other  terminal  of  the  sparking  appliance 
or  to  the  other  end  of  the  imperfect  contact. 

"According  to  my  present  invention  I  inclose  the  receiver  in  a  metallic 
box  A.  One-twentieth  of  an  inch  is  a  suitable  thickness  for  the  metal. 


SHIELDS. 


181 


The  inside  of  the  box  is  connected  by  a  wire  A'  to  the  relay-circuit,  and  its 
outside  by  wires  A2  A3  to  one  terminal  of  the  telegraphic  instrument  h  and 
earth  E,  respectively.  The 
other  branch  of  the  relay- 
circuit  is  connected  by  a 
wire  A4,  insulated  from  the 
box,  to  the  other  terminal 
of  the  instrument  h. 

"  B  is  a  coil  on  the  wire 
A4  and  outside  the  box.  It 
is  protected  from  mechani- 
cal injury  by  a  wooden  case 
C ;  but  this  may  be  omitted. 
The  coil  B  may  contain 
about  twenty  yards  of  wire 
one  seventy-fifth  of  an  inch 
in  diameter  and  have  one 
hundred  and  twenty  turns. 
"The  wire  is  insulated 
with  gutta-percha  D,  which 
is  covered  with  tin-foil  F,  Fig'  7°- 

as  shown  in  Fig.  71.     The  tin-foil  is  in  electric  connection  with 
the  box.      The  coil  B  prevents  oscillations  of  the  transmitter 
Fig.  71.     from  reaching   the   coherer  at    the    same    station    through    the 
wire  A4.     The  aerial  conductor  u  can  be  connected  by  a  flex- 
ible conductor,  plug  G',  and  spring-contacts  H  and  H'  either  to  one  of  the 
balls  e  for  transmitting  or  to  one  end  of  the  tube  j  for  receiving.     The 
other  end  of  the  tube/  is  connected  by  a  wire  J  to  the  inside  of  the  box." 


1 82  WIRELESS    TELEGRAPHY. 


CONDENSERS,     INDUCTANCE-COILS     AND     KEYS. 

To  round  out  this  division  of  the  work  and  to  furnish 
means  of  ready  reference,  there  is  presented  here  a  brief 
account  of  important  principles  and  devices  connected 
with  Wireless  Telegraphy,  which,  however,  are  neither 
novel, nor  peculiar  to  it. 

Condensers.  —  When  a  source  of  electrical  current  is 
connected  to  a  conductor,  a  long  wire  for  instance,  and 
that  conductor  is  insulated  both  along  its  course  and  from 
a  return  wire  or  from  the  earth,  it  will  become  charged. 
Suppose  instead  of  a  long  wire  the  conductor  be  a  small 
sheet  of  tin-foil  positively  charged,  and  suppose  another 
sheet  of  tin-foil  negatively  charged  be  placed  near  the  first 
one,  say,  by  gluing  the  two  sheets  upon  opposite  sides  of 
a  glass  plate,  then  the  amount  of  charge  which  may  be 

spread    upon    the    tin-foil 
sheets  will  be  greatly  in- 
creased.     The  total  quan- 
Fig>  72>  tity    of    electricity    which 

may  thus  be  stored  depends  upon  the  area  of  the  surfaces 
in  the  metal,  upon  the  nearness  to  each  other  of  the  two 
oppositely  charged  sheets,  which  is  to  say  the  thinness  of 
insulation  between  them,  and  also  upon  the  composition  of 
the  insulating  medium  or  "dielectric."  Suppose  two  tin- 
foil sheets  are  joined  together  at  their  edges  and  interlaced 
with  and  insulated  from  two  other  sheets  connected  at  the 
edges,  then  a  diagrammatic  expression  would  be  as  in  Fig. 
72,  that  diagram  being  the  accepted  symbol  for  a  condenser. 
Multiplication  of  sheets  increases,  in  direct  proportion, 


CONDENSERS,    INDUCTANCE-COILS   AND  KEYS.  183 

the  capacity  of  the  condenser  for  the  storage  of  electricity. 
The  amount  stored  is  also  more  or  less  according  to  the 
"  specific  inductive  capacity  "  of  the  insulating  medium  — 
the  "  dielectric."  If  the  effect  of  dry  air  be  taken  as  I, 
that  of  rubber  is  equivalent  to  3,  of  sulphur  to  4,  of  mica 
to  7,  and  of  glass  to  9.  For  convenience  and  economy 
condensers  are  usually  made  of  tin-foil  plates  separated  by 
sheets  of  paraffined  paper  and  sealed  in  a  wood  box. 

Marconi's  Condenser. — Marconi  describes  as  follows 
the  condenser  used  in  connection  with  his  earlier  forms  of 
apparatus  for  "  tuning  "  the  circuit.  "  It  was  composed 
of  six  tin-foil  (or  copper)  plates  connected  to  each  terminal, 
each  plate  being  1.97  inches  by  1.18  inches,  the  plates 
being  insulated  by  paraffined  paper,  .067  inch  thick.  Its 
capacity  measurement  was  one-fourth  of  one  microfarad." 

Tesla  Condenser.  —  As  has  been  shown  already,  the  con- 
denser plays  a  very  important  part  in  Tesla's  wireless 
transmissions.  In  his  sun  motor  patent  shown  in  Fig.  15, 
Part  I.,  he  uses  mica  as  a  dielectric,  and  treats  the  condens- 
ers by  a  process  of  his  own  invention,  consisting  in  inclos- 
ing the  device  in  an  air-tight  receptacle,  exhausting  the  air 
from  the  receptacle,  introducing  into  a  vessel  containing 
the  device  an  insulating  material  rendered  fluid  by  heat, 
and  when  this  material  has  permeated  the  interstices  of 
the  condenser  subjecting  the  whole  to  pressure  which  is 
maintained  until  the  material  has  cooled  and  solidified. 

Improvements Other    inventors    have   improved   this 

process  by  so  contriving  the  method   of  filling  that  the 
molten  insulating  material    solidifies    first  in  the  interior 


1 84 


WIRELESS    TELEGRAPHY. 


parts  of  the  condenser  and  then  on  its  edges.  Paraffin 
wax  is  the  principal  ingredient  of  the  insulating  material 
in  these  later  inventions. 


INDUCTANCE    COILS. 

Illustration  of  Lines  of  Magnetic  Force.  —  Suppose  a 
piece  of  cardboard  be  held  horizontally  so  that  iron  filings 
will  rest  upon  its  surface,  and  that  it  be  pierced  through 
its  center  by  a  vertical  copper  wire.  If  the  free  ends  of 

N 


Fig.  73- 

that  wire  above  and  below  the  card  be  connected  to  the 
poles  of  a  battery,  the  filings  will  arrange  themselves  in 
radiating  lines  as  in  Fig.  73.  The  influences  which  ema- 
nate from  the  wire  are  named  magnetic  lines  of  force,  and 
the  area  over  which  such  influences  are  exerted  is  a  mag- 
netic field. 


CONDENSERS,    INDUCTANCE-COILS   AND    KEYS.   185 

Induction    Between  Two ,  Circuits If  st   second  wire 

with  its  ends  joined  together,  to  make  an  endless  loop,  be 
brought  into  a  magnetic  field,  there  will  be  developed  in 
this  loop  an  electric  current.  If,  while  the  two  wires  are 
in  proximity,  either  the  loop  or  the  battery  circuit  be 
moved  or  the  pressure  in  the  battery  circuit  be  varied,  or 
the  lines  of  force  are  passed  across  the  loop,  or  the  loop 
cuts  them,  or  any  electrical  change  is  made,  an  electric 
circuit  is  set  up  in  the  loop. 

Induction  and  Counter-Force  in  a  Coil.  —  If  a  portion 
of  a  wire  in  a  charged  circuit  be  wound  in  a  coil,  the  lines 
of  force  which  may  emanate  from  any  one  turn  are  cut  by 
the  wires  of  the  other  turns,  and  so  a  varying  current  may 
produce  an  inductive  effect  in  that  coil.  The  counter 
pressure  thus  created  tends  to  stop  the  development  of  the 
flowing  current,  because  the  induced  force  is  opposite  in 
direction  to  the  initial  one ;  but  if  the  flowing  current  be 
broken  or  weakened  or  strengthened,  or  in  any  way 
changed  in  direction  or  in  force,  then  the  secondary 
stream  takes  the  same  direction  as  the  primary  one,  and, 
as  both  work  together,  there  is  a  surge  or  impulse  due 
to  the  sudden  release  of  energy  that  has  previously  been 
bound. 

One  Coil  is  Placed  Within  Another.  —  It  is  the  usual 
practice  to  place  in  the  interior  of  a  coil  of  one  circuit 
turns  of  wire  which  are  part  of  another.  This  arrange- 
ment secures  the  best  results  that  may  be  had  with  coils 
alone,  but  a  still  greater  effect  is  had  by  placing  an  iron 
core  within  the  inner  coil.1 

1  The  analogy  of  inductive  effect  to  the  load  upon  a  vibrating  spring  has  been  illus- 
trated by  Fig.  7,  p.  29,  Part  I. 


186  WIRELESS   TELEGRAPHY. 

One  of  Marconi's  Inductance  Coils.  —  Mr.  Marconi,  de- 
scribing an  inductance,  says  : 

Primary.  —  "  The  primary  is  wound  upon  a  glass  tube 
.635  cm.  (about  i  inch)  in  diameter.  This  primary  wind- 
ing consists  of  two  parallel  windings  of  two  hundred  turns 
each  of  copper  wire  .012  cm.  in  diameter  (about  .005  inch, 
or  No.  36,  B.  &  S.  Gauge),  the  wire  being  insulated  by  a 
single  covering  of  silk.  The  resistance  of  these  two  wind- 
ings in  parallel  is  about  3. 1  ohms." 

Secondary.  —  The  secondary  winding  consists  of  800 
turns  of  a  wire  .005  cm.  (.002  inch)  in  diameter,  having  a 
resistance  of  about  140  ohms,  and  wound  either  over  or 
under  the  primary  winding. 

Another  Marconi  Winding.  —  Another  Marconi  induc- 
tance coil  has  the  secondary  wound  directly  upon  a  glass 
tube  .3  inch  diameter,  the  copper  wire  being  .002  inch 
diameter  with  a  single  silk  covering,  and  making  three 
hundred  and  seventy-five  turns  about  the  tube  with  a 
resistance  of  seventy-nine  ohms.  Over  this  secondary 
is  wound  the  primary  of  copper  wire  .005  inch  in  diameter 
with  a  single  silk  wrapping.  Resistance  seven  and  one- 
tenth  ohms.  Each  of  the  four  windings  described  consists 
of  a  single  layer. 


TRANSMITTING    KEYS KEYS    IN    SECONDARY    CIRCUIT    AND 

CONTACTS    IN    OIL, 

In  the  initial  American  patent  of  Marconi,  filed  Decem- 
ber, 1896,  it  is  said  that  when  working  with  large  amounts 


CONDENSERS,  INDUCTANCE-COILS   AND    KEYS.   l8/ 

of  energy  it  is  better  to  keep  the  primary  circuit  in  con- 
stant operation  and  to  interrupt  the  discharge  of  the 
secondary  ;  moreover,  that  in  such  cases  the  contacts  of 


Fig.  74. 


the  key  should  be  immersed  in  oil,  lest,  owing  to  the 
length  of  the  spark,  the  current  continue  to  pass  after  the 
contacts  have  been  separated.  In  the  DeForest  system 
the  key  contacts  are  also  made  in  oil. 


Pig.  75- 


Fessenden  Key-Contacts.  —  One  of  Mr.  Fessenden's 
inventions  in  keys  is  illustrated  by  a  plan  view,  Fig.  74, 
and  sectional  views,  Fig.  75  and  Fig.  76. 

In  this  transmission  it  is  intended  to  keep  the  generator 
in  continuous  operation,  the  manipulation  of  the  key 
throwing  the  sending  conductor  out  of  tune  with  the 


1 88  WIRELESS   TELEGRAPHY. 

receiving  circuit  of  the  distant  station  by  short-circuiting 
more  or  less  of  the  tuning  device. 

Referring  to  the  figures,  switch  3  is  employed  to  render 
the  generator  inoperative  while  the  apparatus  is  being  used 
as  a  receiver  ;  5  indicates  one  or  more  connected  pairs  of 
parallel  wires  to  form  a,  tuning  grid ;  6  indicates  movable 
contacts  adapted,  to.-  connect  electrically  the  wires  or  con- 
ductors of  each  pair  ;  7  is  a  box  containing  sufficient  oil  to 


7- 


,o 


Fig.  76- 

cover  the  wires  to  a  depth  of  about  one  inch  ;  8  are  spring 
arms  ;  9  are  adjusting  blocks  mounted  in  arms  in  the  cover 
of  the  box ;  and  10,  loa,  lob,  ice,  icd  are  fingers  arranged 
to  be  brought  into  successive  contact  with  one  or  more  of 
the  wires  of  the  grid,  thus  to  shunt  more  or  less  of  the 
capacity  and  self-inductance  of  the  sending  circuit. 


MARCONI'S  TRANSMITTING  KEY  AND  LIGHTNING-GUARD. 

In  Fig.  77  is  shown  a  key  arrangement  devised  by  Mar- 
coni for  two  objects,  first,  because  the  wave-gate  is  often 
charged  with  atmospheric  electricity  which,  when  it  is 
shifted  from  the  transmitting  to  the  receiving  circuit,  is 
liable  to  impart  to  the  operator  and  to  the  coherer  an 
injurious  shock  ;  and,  second,  to  prevent  the  accidental 


CONDENSERS,   INDUCTANCE-COILS   AND    KEYS.  189 

operation  of  the  transmitter  when  the  aerial  conductor  is 
connected  to  receiver.  The  arm  of  the  key  is  prolonged 
beyond  its  pivot,  and  carries  an  insulated  contact  which  is 
permanently  connected  to  the  aerial  conductor.  Below 
this  contact  on  the  base  of  the  instrument  is  the  terminal 
of  the  receiver.  The  arm  is  so  arranged  that  immediately 


Fig.  77- 

after  its  release  by  the  operator,  subsequent  to  the  send- 
ing of  a  message,  it  turns  about  upon  its  pivot,  bringing 
the  above-mentioned  contact  and  terminal  together,  so 
connecting  the  receiver  with  the  aerial  conductor. 

In  the  drawing  b'  and  £4  indicate  the  contacts  of  an 
ordinary  Morse  key  and  a  high  insulating  handle.  The 
extension  arm  b  has  an  insulated  contact  b2.  When  the 
key  is  released  by  the  operator  its  longer  arm  falls  by  its 
own  weight,  the  contact  b2  descending  upon  the  con- 
tact £. 


190 


APPENDIX   I. 


CQ 


— a 


•f 


Plate  Ic 

Reproduction  of  drawing  accompanying  United  States  Patent  of   Amos  E.  Dolbear, 
No.  350,299,  dated  October  5,  1886. 
[See  p.  96.] 


APPENDIX  I. 


UNITED    STATES   PATENT   OFFICE. 

AMOS    EMERSON   DOLBEAR,  OF  SOMERVILLE,   MASSACHUSETTS, 

ASSIGNOR,  BY   MESNE   ASSIGNMENTS,  TO  THE  DOLBEAR 

ELECTRIC  TELEPHONE  COMPANY,  OF  NEW  JERSEY. 

MODE    OF   ELECTRIC   COMMUNICATION. 

Specification  forming  part  of  Letters  Patent  No.  350,299,  dated 
October  5,  1886. 

Application  filed  March  24,  1882.     Serial  No.  56,264.    (No  model.) 

To  all  whom  it  may  concern  : 

Be  it  known  that  I,  AMOS  EMERSON  DOLBEAR,  of  Somerville,  in 
the  county  of  Middlesex  and  State  of  Massachusetts,  have  invented  a 
new  Mode  of  Electric  Communication,  of  which  the  following  is 
a  full,  clear,  concise,  and  exact  description,  reference  being  had  to 
the  accompanying  diagram,  forming  a  part  hereof. 

My  invention  relates  to  establishing  electric  communication  be- 
tween two  or  more  places  without  the  use  of  a  wire  or  other  like 
conductor ;  and  it  consists  in  connecting  the  transmitting-instrument 
with  a  ground  the  potential  of  which  is  considerably  above  the 
normal,  and  the  receiving-instrument  with  a  ground  the  potential 
of  which  is  considerably  below  the  normal,  the  result  being  that  an 
impulse  from  the  transmitter  sufficient  to  cause  the  receiver  to  give 
intelligible  signals  is  transmitted  through  the  earth  without  the  need 
of  any  circuit,  such  as  has  heretofore  been  deemed  essential 

In  the  diagram,  A  represents  one  place  (say  Tufts  College),  and  B 
a  distant  place  (say  my  residence). 

C  is  a  wire  leading  into  the  ground  at  A,  and  D  a  wire  leading  into 
the  ground  at  B. 

G  is  a  secondary  coil,  one  convolution  of  which  is  cut,  the  ends 
thus  formed  being  connected  with  the  poles  of  the  battery/',  which 

191 


I92  APPENDIX    I. 

has  a  number  of  cells  sufficient  to  establish  in  the  wire  C,  which  is 
connected  with  one  terminal  of  the  secondary  coil  G,  an  electro- 
motive force  of,  say,  one  hundred  volts.  G  in  this  instance  also  rep- 
resents an  induction-coil,  T  being  a  microphone-transmitter,  f  its 
primary  circuit,  and  f  its  battery  —  that  is,  the  battery  /'  not  only 
furnishes  the  current  for  the  primary  circuit,  but  also  charges  or  elec- 
trifies the  secondary  coil  G  and  its  terminals  C  and  H'. 

Now,  if  words  be  spoken  in  proximity  to  transmitter  T,  the  vibra- 
tion of  its  diaphragm  will  disturb  the  electric  condition  of  the  coil  G, 
and  thereby  vary  the  potential  of  the  ground  at  A,  and  the  variations 
of  the  potential  at  A  will  cause  corresponding  variations  of  the 
potential  of  the  ground  at  B,  and  the  receiver  R  at  B  will  reproduce 
the  words  spoken  in  proximity  to  transmitter  T,  as  if  the  wires  C  D 
were  in  contact  or  connected  by  a  third  wire.  Electric  communica- 
tion may  be  thus  established  between  points  certainly  more  than  half 
a  mile  apart ;  but  how  much  farther  I  cannot  now  say. 

There  are  various  well-known  ways  of  electrifying  the  wire  C  to  a 
positive  potential  far  in  excess  of  a  hundred  volts,  and  the  wire  D  to 
a  negative  potential  far  in  excess  of  a  hundred  volts. 

In  the  diagram,  H  H'  H2  represent  condensers,  the  condenser  H' 
being  properly  charged  to  give  the  desired  effect.  The  condensers  H 
and  H2  are  not  essential,  but  are  of  some  benefit ;  nor  is  the  con- 
denser H'  essential  when  the  secondary  G  is  otherwise  charged.  I 
prefer  to  charge  all  these  condensers,  as  it  is  of  prime  importance 
to  keep  the  grounds  of  wires  C  and  D  oppositely  electrified,  and 
while,  as  is  obvious,  this  may  be  done  by  either  the  batteries  or  the 
condensers,  I  prefer  to  use  both. 

The  main  difficulty  in  utilizing  my  invention  on  a  large  scale  is 
that  when  there  are  many  spots  corresponding  to  A  and  B  signals 
transmitted  from  any  A  will  go  to  the  nearest  B,  or  to  several  B's, 
depending  upon  proximity  and  other  causes.  One  method  of  obviat- 
ing this  difficulty  is  to  use  a  given  A  only  during  a  certain  assigned 
time  for  communicating  with  a  certain  B,  the  particular  B  being 
arranged  to  receive  communications  only  during  the  assigned  time. 
Thus,  if  there  were  ten  B's  within  a  given  area,  then  the  first  B  might 
be  used  for  the  first  hour,  the  second  B  for  the  next  hour,  and  so  on, 
and  the  first  A  for  the  first  five  minutes  of  the  first  hour,  the  second 
A  for  the  next  five  minutes,  and  so  on,  so  that  either  one  of  the  A's 
might  have  free  communication  with  the  first  B,  each  for  its  assigned 
time  during  the  first  hour,  and  either  A  with  the  second  B,  each  for 
its  assigned  five  minutes  of  the  second  hour,  and  so  on. 


APPENDIX   I.  193 

In  practice  there  will  be  of  course  both  a  receiver  and  transmitter 
at  A  and  B,  proper  switches  being  used  to  bring  either  into  use,  as 
will  be  well  understood  without  description. 

I  have  spoken  only  of  telephone-instruments,  as  these  give  the 
best  results ;  but  any  electric  instruments  may  be  used  capable  of 
utilizing  the  currents  passing  through  the  earth  from  C  to  D,  and  the 
strength  of  such  currents  can  be  largely  increased  by  increasing  the 
positive  potential  of  C  and  the  negative  potential  of  D.  It  will  also 
be  obvious  that  if  the  end  of  coil  G  (shown  in  the  diagram  as  con- 
nected with  one  armature  of  condenser  H')  be  grounded,  and  the  end 
shown  grounded  be  connected  with  the  condenser,  then  C  will  be 
minus,  and  D  must  therefore  be  made  plus. 

What  I  claim  is  — 

The  art  above  described  of  communicating  by  electricity,  consist- 
ing in  first  establishing  a  positive  potential  at  one  ground  and  a  nega- 
tive at  another ;  secondly,  varying  the  potential  of  one  ground  by 
means  of  transmitting  apparatus,  whereby  the  potential  of  the  other 
ground  is  varied  ;  and,  lastly,  operating  receiving  apparatus  by  the 
potential  so  varied,  all  substantially  as  described. 

AMOS  EMERSON   DOLBEAR. 
Witnesses: 

G.  B.  MAYNADIER, 
JOHN  R.  SNOW. 


APPENDIX  II. 


UNITED    STATES    PATENT    OFFICE. 

OLIVER  JOSEPH    LODGE,  OF  LIVERPOOL,  ENGLAND. 
ELECTRIC   TELEGRAPHY. 

Specification  forming  part  of  Letters  Patent  No.  674,846,  dated 
May  21,  1901. 

Application  filed  December  20,  1897.    Serial  No.  662,688.    (No  model.) 

To  all  whom  it  may  concern  : 

Be  it  known  that  I,  OLIVER  JOSEPH  LODGE,  a  subject  of  the 
Queen  of  Great  Britain,  residing  at  Liverpool,  in  the  county  of  Lan- 
caster, England,  have  invented  certain  new  and  useful  Improvements 
in  Electric  Telegraphy,  of  which  the  following  is  a  specification. 

My  invention  relates  to  electric  telegraphy ;  and  it  consists  mainly 
in  utilizing  certain  processes  and  combinations  of  apparatus  whereby 
I  am  enabled  to  demonstrate  the  presence  of,  and  to  indicate  in  a 
receiving-circuit  the  reception  of,  what  are  known  as  "Hertzian 
waves  "  emitted  from  any  suitable  apparatus  at  a  distance  from  the 
receiving-circuit  and  propagated  through  space.  Thus  after  a  suc- 
cession of  electrical  surgings  of  predetermined  duration  have  been 
caused  to  emanate  from  the  emitter  in  accordance  with  the  Morse  or 
other  code  of  telegraphic  signaling  the  same  are  taken  up  in  the 
receiver-circuit  and  so  rendered  intelligible,  and  a  telegraphic  system 
is  thus  obtained. 

My  invention  relates,  further,  to  certain  improvements  in  connec- 
tion with  the  emitting  apparatus,  and  comprises  the  other  improve- 
ments hereinafter  more  particularly  described  and  claimed. 

The  annexed  drawings,  which  are  diagrammatic  representations, 
illustrate  my  invention. 

194 


APPENDIX   II. 


195 


Fig.  1 


Plate  II. 

Reproduction  of  drawing  accompanying  United  States  Patent  of  Oliver  Joseph  Lodge, 
No.  674,846,  dated  May  21,  1901. 


196  APPENDIX    II. 

Figure  i  shows  the  essential  parts  of  one  form  of  emitting  appara 
tus.  Fig.  2  illustrates  one  form,  and  Fig.  3  an  alternative  arrange- 
ment, of  the  apparatus  and  assembly  of  parts  which  constitute  my 
receiving-circuit.  Fig.  4  shows  a  form  of  "coherer,"  and  likewise 
serves  to  illustrate  a  means  for  the  automatic  breaking  down  of  the 
cohesion  resulting  from  the  reception  of  waves  by  the  coherer,  as 
hereinafter  fully  described.  Fig.  5  illustrates  an  alternative  form  of 
coherer,  and  Fig.  6  a  still  further  modified  form  thereof  and  an  alter- 
native means  of  breaking  down  cohesion.  Fig.  7  shows  the  coherer 
and  other  parts  incased  within  a  metallic  covering,  as  hereinafter 
described. 

As  emitter  of  the  Hertzian  waves  for  the  purpose  of  this  invention 
I  may  employ  any  known  or  suitable  device  in  which  a  condenser  or 
Leyden  jar  or  other  electric  capacity  consisting  either  of  a  pair  of 
insulated  plates  or  of  a  single  plate  and  the  earth  is  charged  by  an 
electrical  machine  (such  as  Wimshurst's),  or  a  Ruhmkorff  induction- 
coil,  or  a  battery,  or  any  other  well-known  means,  to  a  high  potential 
and  then  discharged  suddenly  with  a  spark  between  suitably  arranged 
and  prepared  surfaces  in  air  or  in  any  medium,  such  as  oil. 

In  Fig.  i  I  have  shown  a  form  of  emitter  in  which  electricity  is 
supplied  to  a  single  conductor  a  (shown  as  a  sphere,  but  which  may 
be  of  dumb-bell  or  any  other  shape)  suddenly  or  disruptively  by  a 
couple  of  positive  and  negative  sparks  from  knobs  b  and  c  and  there 
left  to  oscillate  and  emit  waves.  A  partial  metallic  inclosure  ^/may 
be  used  to  diminish  waves  in  undesired  directions.  Both  of  these 
arrangements  are  my  invention.  The  more  usual  plan  hitherto  has 
been  to  charge  two  conductors  by  a  pair  of  leading-wires  and  let  them 
spark  into  each  other. 

Referring  now  to  Figs.  2  and  3,  my  receiving-circuit  consists,  essen- 
tially, of  a  coherer  <?,  a  battery/ or  other  suitable  source  of  electrical 
energy,  and  a  telegraphic  receiving  instrument^,  all  in  electrical  con- 
nection, as  shown.  There  is  added  to  these  latter  a  collecting-wire 
/*,  of  any  desired  length,  as  shown  in  Fig.  2,  or  else  a  form  of  Hertz- 
ian resonator,  as  shown  at  i  in  Fig.  3,  the  function  of  either  of  which 
is  to  collect  and  to  convey  to  the  coherer  the  Hertzian  waves  produced 
at  a  distance,  as  aforesaid.  In  some  cases  I  find  that  any  bare  wire 
or  a  connection  to  earth  direct  or  through  the  system  of  gas  or  water- 
pipes,  as  shown  at/  in  P^ig.  2,  will  serve  sufficiently  well  as  a  collector 
or  as  an  assistance  to  the  insulated  collector. 

The  coherer  consists,  essentially,  of  an  organism  whose  electrical 
resistance  diminishes  under  the  influence  of  Hertzian  waves,  but 


APPENDIX    II.  197 

which  returns  to  its  former  amount  when  the  cohered  condition 
brought  about  by  the  electrical  influence  is  broken  down  by  mechan- 
ical tremor. 

One  suitable  form  of  coherer  is  illustrated  in  Fig.  4,  which  was 
introduced  (for  other  purposes)  by  Branly  previous  to  the  year  1894. 
This  arrangement  consists  of  a  pair  of  metallic  points  k,  embedded  in 
metallic  grains  or  powder  /  within  a  glass  tube  m ;  but  it  will  be  un- 
derstood that  I  may  employ  any  other  equivalent  device.  For  exam- 
ple, I  may  seal  the  filings  up  in  vacuum,  as  indicated  in  Fig.  5,  which 
I  have  discovered  increases  and  prolongs  its  sensitiveness,  or  I  may, 
as  illustrated  in  Fig.  6,  use  a  coherer  consisting  of  a  needle-point  ;/» 
resting  lightly  on  a  flat  plate  or  spring  o,  fixed  in  a  clamp  j/,  the  de- 
gree of  pressure  being  obtained  by  the  adjustment-screws  p  and  q. 
On  the  arrival  of  Hertzian  waves  more  complete  contact  or  cohesion 
is  set  up  between  the  particles  of  powder  /  or  between  the  point  n 
and  spring  or  other  light  metallic  contact  o,  and  so  allows  more  cur- 
rent from  the  battery /"to  flow  through  the  telegraphic  receiving  in- 
strument (indicated  at  g,  Figs.  2,  3,  and  7) ;  but  then  before  the 
coherer  is  again  in  a  fit  state  to  receive  fresh  impulses,  the  said  cohe- 
sion must  be  destroyed.  Now  according  to  my  invention  I  provide 
for  this  being  effected  by  an  automatic  vibrator.  This  mechanical 
vibration  may  consist  of  a  succession  of  jars  or  knocks  or  taps,  which 
may  be  produced  by  electrical  means,  as  in  an  electric  trembling  bell 
(see  r  in  Fig.  4),  or  by  clockwork  (see  Fig.  6).  In  the  last-mentioned 
figure,  s  and  /  represent  two  wheels  of  a  clockwork-train.  Upon  the 
arbor  (or  on  a  disk  mounted  thereon)  of  the  wheel  s  is  a  series  of 
serrations  or  the  like  u  (shown  exaggerated  in  the  drawings),  which 
as  the  wheel  rotates  effects  the  vibration  of  the  lever  or  spring  o 
either  directly  or  indirectly  through  the  stand.  Such  a  tapper  as  is 
used  in  dentistry  also  serves  very  well  for  my  purpose. 

A  coherer  is  sensitive  not  only  to  the  desired  impulse  arriving  from 
a  distance  and  conveyed  to  it  by  the  collectors,  but  it  is  also  liable  to 
respond  to  any  local  sparks  or  electric  surgings  in  its  neighborhood, 
especially  to  oscillations  in  an  adjacent  emitter.  It  may  be  protected 
from  all  these  by  complete  inclosure  in  a  flawless  metallic  box. 

For  the  purpose  of  protecting  the  coherer  from  undesired  disturb- 
ance, therefore,  I  inclose  it  (sometimes  with  all  coils,  wires,  batteries, 
and  the  like  connected  to  it)  in  a  metallic  covering  or  case,  as  shown 
at  v  in  Fig.  7,  leaving  only  one  or  more  round  holes  or  short  tubes  iv 
for  the  collector  terminal  or  terminals  to  enter  by,  and  for  vision  or 
other  needful  purpose  requiring  an  aperture,  for  through  round  holes 


1 98  APPENDIX   II. 

of  moderate  size  large  electric  waves  do  not  readily  pass,  whereas 
through  chinks  or  long  slits,  no  matter  how  infinitely  narrow,  they  can 
pass  with  ease.  They  likewise  pass  in  by  means  of  any  insulated 
wire  which  enters  the  box ;  but  through  any  wire  which  is  thoroughly 
joined  to  the  metal  wall  of  the  box  where  it  enters  the  waves  cannot 
pass. 

In  the  particular  arrangement  shown  in  Fig.  7  a  single  terminal  h 
is  employed  which  is  insulated  from  the  casing  by  tube  w  and  is  con- 
nected to  one  terminal  only  of  the  coherer.  This  construction  is 
effective  and  desirable  in  certain  cases,and  it  is  found  that  the  Hertz- 
ian waves  pass  in  as  readily  through  the  single  wire,  affecting  the 
coherer  in  the  same  way  as  in  the  case  of  the  earthed  circuit  through 
j  in  Fig.  2.  Hence  it  is  not  absolutely  necessary  to  remove  the  ter- 
minal h  from  its  aperture  when  it  is  not  being  used  for  the  purpose 
of  establishing  communication  and  enabling  waves  from  the  collector 
to  enter  the  box  and  reach  the  coherer ;  for  these  same  terminals  h 
or  j  may  when  they  are  raised  completely  plug  with  metallic  con- 
tinuity, as  shown  at  x,  the  small  holes  through  which  they  can  freely 
afterward  be  lowered. 

The  only  part  of  the  coherer  or  detector  portion  outside  the  box 
(shown  in  Fig.  7)  is  the  index  or  needle  mirror  z  of  the  telegraphic 
receiving  instrument  employed,  which  is  acted  upon  and  deflected  by 
its  coil  £•  inside  acting  magnetically  through  the  metal  wall. 

When  the  plan  of  withdrawing  the  terminals  of  the  box  is  adopted, 
it  is  sufficient  to  put  the  coherer  above  mentioned  alone  in  the  box. 

What  I  claim,  and  desire  to  secure  by  Letters  Patent  of  the  United 
States,  is: 

1.  In  a  system  of  Hertzian-wave  telegraphy,  an  emitter  consisting 
of  a  single  conducting  body  and  means  for  suddenly  and  disruptively 
communicating  opposite   electric  charges   thereto,  whereby  oscilla- 
tions are  set  up  in  said  body,  and  waves  are  emitted,  substantially  as 
described. 

2.  In  a  system  of  Hertzian-wave  telegraphy,  an  emitter  comprising 
a  single  conductor  supplied  with  opposite  electricities  by  a  pair  of 
knobs  connected  to  the  terminals  of  a  high-potential  source. 

3.  In  a  system  of  Hertzian-wave  telegraphy,  the  combination  with 
an  emitter,  of  a  partial  metallic  inclosure  serving  to  lessen  the  emis- 
sion of  Hertzian  waves  in  undesired  directions. 

4.  A  coherer  comprising  a  variable  electrical  contact  sealed  in 
vacuum. 

5.  In  a  receiver  for  Hertzian-wave  signaling  systems,  the  combina- 


APPENDIX   II.  199 

tion  of  the  following  instrumentalities :  a  coherer,  a  base  or  support 
upon  which  it  is  mounted,  and  a  vibrator  mounted  in  proximity  to  the 
coherer,  and  adapted  to  agitate  its  elements. 

6.  In  the  receiving-circuit  of  a  system  of  Hertzian-wave  telegraphy, 
the  combination,  with  a  coherer,  of  automatic  means  to  successively 
break  down  the  cohesion  caused  in  said  coherer  by  such  Hertzian 
waves. 

7.  In  combination,  in  the  receiving-circuit  of  a  system  of  Hertzian- 
wave  telegraphy,  a  coherer,  a  battery,  a  telegraphic  receiving  instru- 
ment, and  automatic  means  to  successively  break  down  the  cohesion 
caused  in  said  coherer  by  such  Hertzian  waves. 

8.  In  combination,  in  the  receiving-circuit  of  a  system  of  Hertzian- 
wave  telegraphy,  a  coherer,  a  battery,  a  telegraphic  receiving  instru- 
ment, automatic  means   to  successively  break  down   the   cohesion 
caused  in  said  coherer  by  such  Hertzian  waves,  and  means  serving 
to  collect  and  convey  to  the  coherer  Hertzian  waves  produced  at  a 
distance. 

In  testimony  whereof  I  have  hereunto  subscribed  my  name. 

OLIVER  JOSEPH    LODGE. 
Witnesses: 

WM.  PIERCE, 
WM.  G.  MURRAY. 


APPENDIX  III. 


UNITED    STATES    PATENT   OFFICE. 

GUGLIELMO  MARCONI,  OF  LONDON,  ENGLAND,  ASSIGNOR,  BY  MESNE 

ASSIGNMENTS,  TO   MARCONI'S   WIRELESS   TELEGRAPH 

COMPANY,   LIMITED,   OF   ENGLAND. 

TRANSMITTING   ELECTRICAL   IMPULSES    AND    SIGNALS 
AND   APPARATUS   THEREFOR. 

Specifications  forming  part  of  Reissued  Letters  Patent  No.  11,913, 
dated  June  4,  1901. 

Original  No.  586,193,  dated  July  13,  1897.     Application  for  reissue  filed  April  i,  1901. 
Serial  No.  53,896. 

To  all  whom  it  may  concern  : 

Be  it  known  that  I,  GUGLIELMO  MARCONI,  a  subject  of  the  King 
of  Italy,  residing  and  having  a  post-office  address  at  18  Pinch  Lane, 
Threadneedle  Street,  London,  England,  have  invented  certain  new 
and  useful  Improvements  in  Transmitting  Electrical  Impulses  and 
Signals  and  in  Apparatus  Therefor,  of  which  the  following  is  a 
specification. 

According  to  this  invention  electrical  signals,  actions,  or  manifes- 
tations are  transmitted  (through  the  air,  earth,  or  water)  by  means  of 
oscillations  of  high  frequency,  such  as  have  been  called  "  Hertz 
rays"  or  "Hertz  oscillations."  All  line-wires  may  be  dispensed 
with.  At  the  transmitting-station  I  preferably  employ  a  Ruhmkorff 
coil,  having  in  its  primary  circuit  a  Morse  key  or  other  signaling 
instrument  and  at  its  poles  appliances  for  producing  the  desired 
oscillations.  The  Ruhmkorff  coil  may,  however,  be  replaced  by  any 
other  source  of  high-tension  electricity.  When  working  with  large 
amounts  of  energy,  it  is,  however,  better  to  keep  the  coil  or  trans- 


APPENDIX    III. 


201 


Fig.  1 


ci 

/             r 
-/' 

d3\            Id3 
••     2ra  r~rirn  ^ihrfi  ?«  -  - 

,c1 

B-^;  vtv-yiH;  4 

d*  d  e'  d2\~d  d 

/: 

D 

Plate  III. 

Reproduction  of  first  sheet  of  drawings  accompanying  United  States  Patent  of 
Guglielmo  Marconi,  No.  11,913.     (A  reissue.) 


2O2 


APPENDIX    III. 


fr- 


Fig,  4 


Fig.  5 


o     k 


Plate  IV. 

Reproduction  of  second  sheet  of  drawings  accompanying  United  States  Patent  of 
Guglielmo  Marconi,  No.  11,913.     (A  reissue.) 


APPENDIX   III. 


203 


Fig.  10 


Fig.  11 


Reproduction  of  third  sheet  of  drawings  accompanying  United  States  Patent  of 
Guglielmo  Marconi,  No.  11,913.     (A  reissue.) 


204  APPENDIX    III. 

former  constantly  working  for  the  time  during  which  one  is  trans- 
mitting, and  instead  of  interrupting  the  current  of  the  primary 
interrupting  the  discharge  of  the  secondary.  In  this  case  the  con- 
tacts of  the  key  should  be  immersed  in  oil,  as  otherwise,  owing  to  the 
length  of  the  spark,  the  current  will  continue  to  pass  after  the 
contacts  have  been  separated.  At  the  receiving-station  there  is  a 
local-battery  circuit  containing  any  ordinary  receiving  instrument 
and  an  appliance  for  closing  the  circuit,  the  latter  being  actuated  by 
the  oscillations  from  the  transmitting-station.  When  transmitting 
through  the  air,  and  it  is  desired  that  the  signal  should  only  be  sent 
in  one  direction,  I  place  the  oscillation-producer  at  the  transmitting- 
station  in  the  focus  or  focal  line  of  a  reflector  directed  to  a  receiv- 
ing-station, and  I  place  the  circuit-closer  at  the  receiving-station  in  a 
similar  reflector  directed  toward  the  transmitting-station.  When 
transmitting  signals  by  the  aid  of  earth  connections,  I  connect  one 
end  of  the  oscillation-producer  and  one  end  of  the  circuit-closer  to 
earth  and  the  other  ends  to  plates  preferably  electrically  tuned  with 
each  other  in  the  air  and  insulated  from  earth. 

Figure  i  is  a  diagrammatic  front  elevation  of  the  instruments  at 
the  transmitting-station  when  signaling  through  the  air,  and  Fig.  2  is 
a  vertical  section  of  the  transmitter.  Fig.  2a  is  a  longitudinal  section 
of  the  oscillator  to  a  larger  scale.  Fig.  3  shows  a  detail  of  the 
trembler-break  on  a  larger  scale.  Fig.  4  is  a  diagrammatic  front 
elevation  of  the  instruments  at  the  receiving-station.  Fig.  5  is  an 
enlarged  view  of  the  receiver.  Fig.  6  shows  a  modification  of  the 
tube  j.  Fig.  7  shows  the  detector.  Fig.  8  is  a  full-sized  view  of 
the  liquid  resistance.  Figs.  9  and  10  show  modifications  of  the 
arrangements  at  the  transmitting-station.  Fig.  u  shows  a  modifica- 
tion of  the  arrangements  at  the  receiving-station. 

Referring  now  to  Fig.  i,  a  is  a  battery,  and  b  an  ordinary  Morse 
key  closing  the  circuit  through  the  primary  of  a  Ruhmkorff  coil  c. 
The  terminals  c'  of  the  secondary  circuit  of  the  coil  are  connected  to 
two  metallic  balls  dd,  fixed  by  heat  or  otherwise  at  the  ends  of 
tubes  d'  d',  Fig.  2a,  of  insulating  material,  such  as  ebonite  or  vulcan- 
ite, e  e  are  similar  balls  fixed  in  the  other  ends'of  the  tubes  d'.  The 
tubes  d'  fit  tightly  in  a  similar  tube  d*,  having  covers  d*,  through 
which  pass  rods  d^,  connecting  the  balls  d  to  the  conductors.  One 
(or  both)  of  the  rods  d^  is  connected  to  the  ball  d  by  a  ball-and- 
socket  joint  and  has  a  screw-head  upon  it  working  in  a  nut  in  the 
cover  d*.  By  turning  the  rod,  therefore,  the  distance  of  the  balls  e 
apart  can  be  adjusted,  d5  represents  holes  in  the  tube  d*,  through 


APPENDIX    III.  205 

which  vaseline,  oil,  or  like  material  is   introduced  into  the  space 
between  the  balls  e. 

-The  balls  d  and  e  are  preferably  of  solid  brass  or  copper,  and  the 
distance  they  should  be  apart  depends  on  the  quantity  and  electromo- 
tive force  of  the  electricity  employed,  the  effect  increasing  with  the 
distance  so  long  as  the  discharge  passes  freely.  With  a  coil  giving 
an  ordinary  eight-inch  spark,  the  distance  between  e  and  e  should,  to 
assure  good  results,  be  from  one  twenty-fifth  to  one-thirtieth  of  an 
inch,  and  the  distance  between  d  and  e  about  one  and  one-half 
inches.  Other  conditions  being  equal,  the  larger  the  balls  the  greater 
is  the  distance  at  which  it  is  possible  to  communicate.  I  have  gen- 
erally used  balls  of  solid  brass  of  four  inches  diameter,  giving  oscilla- 
tions of  ten  inches  length  of  wave. 

If  a  very  powerful  source  of  electricity  giving  a  very  long  spark  be 
employed,  it  is  preferable  to  divide  the  spark-gap  between  the  central 
balls  of  the  oscillator  into  several  smaller  gaps  in  series.  This 
may  be  done  by  introducing  between  the  big  balls  smaller  ones  of 
about  half  an  inch  diameter,  held  in  position  by  ebonite  frames. 

I  find  that  the  regularity  and  power  of  the  discharge  of  an  ordi- 
nary Ruhmkorff  coil  with  a  trembler-break  on  its  primary  is  greatly 
improved  by  causing  one  of  the  contacts  of  the  vibrating  break  to 
revolve  rapidly.  I  do  this  preferably  by  having  a  revoluble  central 
core  r2,  Fig.  3,  in  an  ordinary  screw  £3,  which  is  in  communication 
with  platinum  contacts.  I  cause  the  said  central  core,  with  one  of 
the  platinum  contacts  attached  to  it,  to  revolve,  preferably,  by  con- 
necting it  to  a  small  electric  motor  <*.  This  motor  can  be  worked  by 
the  same  circuit  that  works  the  coil,  or,  if  necessary,  by  a  separate 
circuit.  The  connections  are  not  shown  in  the  drawings.  By  this 
means  the  platinums  are  kept  smooth,  and  any  tendency  to  stick  is 
removed.  They  last,  also,  much  longer.  At  the  receiving-station 
is  a  battery  whose  circuit  includes  an  ordinary  telegraphic  instru- 
ment (or  it  may  be  a  relay  or  other  apparatus  which  is  desired  to 
work  from  a  distance)  and  a  circuit-closer. 

In  Fig.  4,^  is  the  battery,  and  h  a  telegraphic  instrument  on  the 
derived  circuit  of  a  relay  n. 

The  appliance  I  employ  as  a  circuit-closer  is  shown  at  Fig.  5,  and 
consists  of  a  glass  tube  /,  containing  metallic  powder  or  grains  of 
metal  /',  each  end  of  the  column  of  powder  being  connected  to  a 
metallic  plate  k  of  suitable  length  to  cause  the  system  to  resonate 
electrically  in  unison  with  the  electrical  oscillations  transmitted. 
The  glass  tube  may  be  replaced  in  some  places  by  one  of  gutta- 


206    '  APPENDIX   III. 

percha  or  like  material.  Two  short  pieces  /2,  preferably  of  thick 
silver  wire  of  the  same  diameter  as  the  internal  diameter  of  the 
tube/,  so  as  to  fit  tightly  in  it,  are  joined  to  two  pieces  of  platinum 
wire  /3.  The  tube  is  closed  and  sealed  onto  the  platinum  wires/3  at 
both  ends. 

Many  metals  can  be  employed  for  producing  the  powder  or 
filings/';  but  I  prefer  to  use  a  mixture  of  two  or  more  different 
metals.  I  find  hard  nickel  to  be  the  best  metal,  and  I  prefer  to  add 
to  the  nickel  filings,  about  ten  per  cent  of  hard-silver  filings,  which 
increase  greatly  the  sensitiveness  of  the  tube  to  electric  oscillations. 
By  increasing  the  proportion  of  silver  powder  or  grains  the  sensitive- 
ness of  the  tube  also  increases  ;  but  it  is  better  for  ordinary  work  not 
to  have  a  tube  of  too  great  sensitiveness,  as  it  might  be  influenced  by 
atmospheric  or  other  electricity.  The  sensitiveness  can  also  be 
increased  by  adding  a  very  small  amount  of  mercury  to  the  filings 
and  mixing  up  until  the  mercury  is  absorbed. 

The  mercury  must  not  be  in  such  a  quantity  as  to  clot  or  cake  the 
filings.  An  almost  imperceptible  globule  is  sufficient  for  a  tube.  In- 
stead of  mixing  the  mercury  with  the  powder  one  can  obtain  the  same 
effects  by  slightly  amalgamating  the  inner  surfaces  of  the  plugs 
which  are  to  be  in  contact  with  the  filings.  Very  little  mercury  must 
be  used,  just  sufficient  to  brighten  the  surface  of  the  metallic  plugs 
without  showing  any  free  globules.  The  size  of  the  tube  and  the 
distance  between  the  two  metallic  stops  may  vary  under  certain 
limits.  The  greater  the  space  allowed  for  the  powder  the  larger  and 
coarser  ought  to  be  the  filings  or  grains. 

I  prefer  to  make  my  sensitive  tubes  of  the  following  size :  The 
tube  /  is  one  and  one-half  inches  long  and  one-tenth  or  one-twelfth 
of  an  inch  in  internal  diameter.  The  length  of  the  stops/2  is  about 
one-fifth  of  an  inch,  and  the  distance  between  the  stops  is  about  one- 
thirtieth  of  an  inch.  I  find  that  the  smaller  the  space  between  the 
stops  in  the  tube  the  more  sensitive  it  proves ;  but  the  space  cannot 
under  ordinary  circumstances  be  excessively  shortened  without  in- 
juring the  fidelity  of  the  transmission. 

The  metallic  powders  ought  not  to  be  fine,  but,  rather,  as  coarse 
as  can  be  produced  by  a  large  and  rough  file. 

All  the  very  fine  powder  ought  to  be  removed  by  blowing  or 
sifting. 

The  powder  ought  not  to  be  compressed  between  the  stops,  but 
rather,  loose,  and  in  such  a  condition  that  when  the  tube  is  tapped 
the  powder  may  be  seen  to  move. 


APPENDIX   III.  207 

The  tube  must  be  sealed ;  but  a  vacuum  inside  it  is  not  essential 
A  slight  vacuum,  however,  results  from  having  heated  it  while  sealing 
it.  Care  must  also  be  taken  not  to  heat  the  tube  too  much  in  the 
center  when  sealing  it,  as  it  would  oxidize  the  surfaces  of  the  silver 
stops  and  also  the  powder,  which  would  diminish  its  sensitiveness. 
I  use  in  sealing  the  tubes  a  hydrogen  and  air  flame.  A  vacuum  is, 
however,  desirable,  and  I  have  used  one  of  about  one  one-thousandth 
of  an  atmosphere,  obtained  by  a  mercury-pump.  It  is  also  necessary 
for  the  powder  or  grains  to  be  dry  and  free  from  grease  or  dirt,  and 
the  files  used  in  producing  the  same  ought  to  be  frequently  washed 
and  dried,  and  used  when  warm. 

If  the  tube  has  been  well  made,  it  should  be  sensitive  to  the 
induction  of  an  ordinary  electric  bell  when  the  same  is  working  at 
one  to  two  yards  or  more  from  the  tube. 

In  order  to  keep  the  sensitive  tube  j  in  good  working  order,  it  is 
desirable,  but  not  absolutely  necessary,  not  to  allow  more  than  one 
milliampere  to  flow  through  it  when  active.  If  a  stronger  current  is 
necessary,  several  tubes  may  be  put  in  derivation  between  the  tuned 
plates ;  but  this  arrangement  is  not  quite  as  satisfactory  as  the  single 
tube.  It  is  necessary  when  using  tubes  of  the  type  I  have  described 
not  to  insert  in  the  circuit  more  than  one  coil  of  the  Leclanche  type, 
as  a  higher  electromotive  force  than  1.5  volts  is  apt  to  pass  a  current 
through  the  tube  even  when  no  oscillations  are  transmitted.  I  can, 
however,  construct  tubes  capable  of  working  with  a  much  higher 
electromotive  force.  Fig.  6  shows  one  of  these  tubes.  In  this  tube 
instead  of  one  space  or  gap  filled  with  filings  there  are  several  spaces 
separated  by  sections  of  tight-fitting  silver  wire.  A  tube  thus  con- 
structed, observing  also  the  rules  of  construction  of  my  tubes  in 
general,  will  work  satisfactorily  if  the  electromotive  force  of  the 
battery  in  circuit  with  the  tube  is  equal  to  1.2  volts  multiplied  by  the 
number  of  gaps.  With  this  tube,  also,  it  is  well  not  to  allow  a 
current  of  more  than  one  milliampere  to  pass. 

The  tube/ may  be  replaced  by  other  forms  of  imperfect  electrical 
contacts. 

The  plates  k  are  of  copper  or  aluminium  or  other  metal,  about 
half  an  inch  or  more  broad,  about  one-fiftieth  of  an  inch  thick,  and 
preferably  of  such  a  length  as  to  be  electrically  tuned  with  the  electric 
oscillations  transmitted.  The  means  I  adopt  for  fixing  the  length 
of  the  plates  is  as  follows :  I  stick  a  rectangular  strip  of  tin-foil  m 
(see  Fig.  7)  about  twenty  inches  long  (the  length  depends  on  the 
supposed  length  of  wave  that  one  is  measuring),  by  means  of  a  weak 


2o8  APPENDIX   III. 

solution  of  gum,  onto  a  glass  plate  ///'.  Then  by  means  of  a  very 
sharp  penknife  or  point,  I  cut  across  the  middle  of  the  tin-foil,  leav- 
ing a  mark  of  division  m*.  If  this  detector  is  held  in  the  proximity 
(four  or  five  yards)  and  parallel  with  the  axis  of  the  oscillator  in 
action  it  will  show  little  sparks  at  m^.  If  the  length  of  the  pieces  of 
tin-foil  approximates  to  the  length  of  wave  emitted  from  the  oscil- 
lator, the  spark  will  take  place  between  them  at  a  certain  distance 
from  the  transmitter,  which  is  a  maximum  when  they  are  of  suitable 
length.  By  shortening  or  lengthening  the  strips,  therefore,  it  is  easy  to 
find  the  length  most  appropriate  to  the  length  of  wave  emitted  by  the 
oscillator.  It  is  desirable  to  try  this  detector  in  the  focus  or  focal 
line  of  the  reflector.  The  length  so  found  is  the  proper  length  for 
the  plates  k,  or  rather  these  should  be  about  half  an  inch  shorter  on 
account  of  the  length  of  the  sensitive  tube  /,  connected  between 
them. 

Instead  of  the  tuned  plates,  k  tubes  or  even  wires  may  be  em- 
ployed. 

f  is  a  cylindrical  parabolic  reflector  made  by  bending  a  metallic 
sheet,  preferably  of  brass  or  copper,  to  form  and  fixing  it  to  metallic 
or  wooden  ribs/7. 

/  is  a  cylindrical  parabolic  reflector  similar  to  that  used  at  the 
transmitting-station. 

The  reflectors  applied  to  the  receiver  and  transmitter  ought  to  be, 
preferably,  in  length  and  opening,  the  double  at  least  of  the  length  of 
wave  emitted  from  the  oscillator. 

It  is  slightly  advantageous  for  the  focal  distance  of  the  reflector  at 
the  receiving-station  to  be  equal  to  one-fourth  or  three-fourths  of  the 
wave  length  of  the  oscillation  transmitted. 

I  have  hitherto  only  mentioned  the  use  of  cylindrical  reflectors; 
but  it  is  also  possible  to  use  ordinary  concave  reflectors,  preferably 
parabolic,  such  as  are  used  for  projectors. 

It  is  not  essential  to  have  a  reflector  at  the  transmitters  and  re- 
ceivers ;  but  in  their  absence  the  distance  at  which  one  can  communi- 
cate is  much  smaller. 

When  no  oscillations  are  sent  from  the  transmitting-station,  the 
tube  j  does  not  conduct  the  current  and  the  local-battery  circuit  is 
broken;  but  when  the  powder  or  tube  is  influenced  by  the  electrical 
oscillations  from  the  transmitter  it  conducts  and  closes  the  circuit. 
I  find,  however,  that  when  once  started  the  powder  in  the  tube  con- 
tinues to  conduct  even  when  the  oscillations  from  the  transmitter 
have  ceased  ;  but  if  it  be  shaken  or  tapped  the  circuit  is  broken.  A 


APPENDIX    III.  209 

tube  well  prepared  will  instantly  interrupt  tne  current  passing 
through  it  at  the  slightest  tap,  provided  it  is  inserted  in  a  circuit 
i-n  which  there  is  little  self-induction  and  small  electromotive 
force,  such  as  a  single  cell,  and  where  the  effects  of  self-induction 
have  been  removed  by  one  of  the  methods  which  I  will  presently 
describe. 

The  two  plates  k  communicate  with  the  local  circuit  through  two 
very  small  coils  £',  which  I  will  call  "  choking-coils,"  formed  by 
winding  a  few  inches  of  very  thin  and  insulated  copper  wire  around 
a  bit  of  iron  wire  about  an  inch  and  a  half  long.  The  object  of  these 
choking-coils  is  to  prevent  the  high-frequency  oscillation  induced 
across  these  plates  by  the  transmitter  from  dissipating  itself  by  run- 
ning along  the  local-battery  wires,  which  might  weaken  its  effect  on 
the  sensitive  tube/  These  choking-coils  may,  however,  be  some- 
times replaced  by  simple  thin  wires.  They  may  also  be  connected 
directly  to  the  tube/  The  local  circuit  in  which  the  sensitive  tube/ 
is  inserted,  contains  a  sensitive  relay  «,  preferably  wound  to  a  resis- 
tance of  about  twelve  hundred  ohms.  This  resistance  need  not  be 
necessarily  that  of  the  relay,  but  may  be  the  sum  of  the  resistance  of 
the  relay  and  another  additional  resistance.  The  relay  ought  to  be 
one  possessing  small  self-induction. 

The  plates  £,  tube/  and  coils  k'  are  fastened  by  means  of  wire 
stitches  o'  to  a  thin  glass  tube  o,  preferably  not  longer  than  twelve 
inches,  firmly  fixed  at  one  end  to  a  strong  piece  of  timber  02.  This 
may  be  done  by  means  of  wood  or  ebonite  grasping-screws. 

I  do  the  tapping  automatically  by  the  current  started  by  the  tube, 
employing  a  trembler^  on  the  circuit  of  the  relay;;  similar  in  con- 
struction to  that  of  an  electric  bell,  but  having  a  shorter  arm.  This 
vibrator  must  be  carefully  adjusted.  Preferably  the  blows  should  be 
directed  slightly  upward  to  prevent  the  filings  from  getting  caked. 
In  place  of  tapping  the  tube,  the  powder  can-be  disturbed  by  slightly 
moving  outward  and  inward  one  or  both  of  the  stops/2,  the  trembler 
being  replaced  by  a  small  electromagnet  (or  magnets)  whose  arma- 
ture is  connected  to  the  stop. 

I  ordinarily  work  the  telegraphic  receiver  h  (or  other  instruments) 
by  a  derivation,  as  shown,  from  the  circuit  which  works  the  trembler 
p.  They  can  also,  however,  be  worked  in  series  with  the  trembler. 
When  working  ordinary  sounders  or  Morse  apparatus,  a  special 
adjustment  of  the  same  is  sometimes  needed  to  enable  one  to  obtain 
dots  and  dashes.  Sometimes  it  is  necessary  to  work  the  telegraphic 
instruments  or  relays  from  the  back  stops  of  the  first  relay,  as  is  done 


2io  APPENDIX    III. 

in  some  systems  of  multiple  telegraphy.  Such  adjustments  are  known 
to  telegraphic  experts. 

By  means  of  a  tube  with  multiple  gaps  it  is  possible  to  work  the 
trembler  and  also  the  signaling  or  other  apparatus  direct  on  the  cir- 
cuit which  contains  the  tube  ;  but  I  prefer,  when  possible,  to  work- 
with  the  single-gap  tube  and  the  relay,  as  shown.  With  a  sensitive 
and  well-constructed  trembler  it  is  also  possible  to  work  the  trembler 
with  the  single-gap  tube  in  series  with  it  without  the  relay. 

In  derivation  on  the  terminals  of  the  relay  n  is  placed  an  ordinary 
platinoid  resistance  double-wound  (or  wound  on  the  "bight,"  as  it 
is  sometimes  termed)  coil  q  of  about  four  times  the  resistance  of  the 
relay,  which  prevents  the  self-induction  of  the  winding  of  the  relay 
from  affecting  the  sensitive  tube. 

The  circuit  actuated  by  the  relay  contains  an  ordinary  battery  r  of 
about  twelve  cells  and  the  trembler/,  the  resistance  of  the  winding 
of  which  should  be  about  one  thousand  ohms,  and  the  core  ought 
preferably  to  be  of  soft  iron,  hollow  and  split  lengthwise,  like  most 
electromagnets  used  in  telegraph  instruments.  In  series  or  deriva- 
tion from  this  circuit  is  inserted  the  telegraphic  or  other  apparatus  /;, 
which  one  may  desire  to  work.  It  is  desirable  that  this  instrument 
or  apparatus,  if  on  a  derivation,  should  have  a  resistance  equal  to  the 
resistance  of  the  trembler/.  A  platinoid  resistance  h'  of  about  five 
times  the  resistance  of  the  instrument  is  inserted  in  derivation  across 
the  terminals  of  the  instrument  and  connected  as  close  to  the  same  as 
possible.  In  derivation  across  the  terminals  of  the  trembler  p  is 
placed  another  platinoid  resistance  /',  also  of  about  five  times  the 
resistance  of  the  trembler.  A  similar  resistance  ft2"  is  inserted  in  a 
circuit  connecting  the  vibrating  contacts  of  the  trembler.  In  deriva- 
tion across  the  terminals  of  the  relay-circuit  it  is  well  to  have  a  liquid 
resistance  s,  which  is  constituted  of  a  series  of  tubes,  one  of  which  is 
shown  full  size  in  Fig.  8,  filled  with  water  acidulated  with  sulfuric 
acid.  The  number  of  these  tubes  in  series  across  the  said  terminals 
ought  to  be  about  ten  for  a  circuit  of  fifteen  volts,  so  as  to  prevent,  in 
consequence  of  their  counter  electromotive  force,  the  current  of  the 
local  battery  from  passing  through  them,  but  allowing  the  high-ten- 
sion jerk  of  current  generated  at  the  opening  of  the  circuit  in  the 
relay  to  pass  smoothly  across  them  without  producing  perturbing 
sparks  at  the  movable  contact  of  the  relay.  It  is  also  necessary  to 
insert  a  platinoid  resistance  in  derivation  on  any  apparatus  one  may 
be  working  on  the  local  circuits.  These  resistances  ought  also  to  be 
inserted  in  derivation  on  the  terminals  of  any  resistance  which  may 
be  apt  to  give  self-induction. 


APPENDIX   III.  2ii 

I  find  it  convenient  when  transmitting  across  long  distances  to 
make  use  of  the  transmitter  shown  in  Fig.  9. 

/  /  are  two  poles  connected  by  a  rope  /',  to  which  are  suspended, 
by  means  of  insulating-suspenders,  two  metallic  plates  /2  /2,  prefer- 
ably in  the  form  of  cylinders  closed  at  the  top,  connected  to  the 
spheres  e  (in  oil  or  other  dielectric,  as  before)  and  to  the  other  balls 
/3  in  proximity  to  the  spheres  c' ,  in  communication  with  the  coil  or 
transformer  c.  The  balls  /3  are  not  absolutely  necessary,  as  the 
plates  P  may  be  made  to  communicate  with  the  coil  transformer  by 
means  of  thin  insulated  wires.  The  receiver  I  adopt  with  this  trans- 
mitter is  similar  to  it,  except  that  the  spheres  e  are  replaced  by  the 
sensitive  tube  j  and  plates  /£,  while  the  spheres  /3  are  replaced  by 
the  choking-coils  /£',  in  communication  with  the  local  circuit.  It  may 
be  observed  that,  other  conditions  being  equal,  the  larger  the  plates 
at  the  transmitter  and  receiver,  and  the  higher  they  are  from  the 
earth,  and  to  a  certain  extent  the  farther  apart  they  are  the  greater  is 
the  distance  at  which  correspondence  is  possible. 

When  transmitting  with  connections  to  the  earth  or  water,  I  use  a 
transmitter  as  shown  in  Fig.  10.  I  connect  one  of  the  spheres  d  to 
earth  E,  preferably  by  thick  wire,  and  the  other  to  a  plate  or  elevated 
conductor  «,  carried  by  a  pole  v  and  insulated  from  earth  ;  or  the 
sphere  d  may  be  omitted  and  one  of  the  spheres  e  be  connected  to 
earth,  and  the  other  to  the  plate  or  conductor  u.  At  the  receiving- 
station,  Fig.  u,  I  connect  one  terminal  of  the  sensitive  tube/ to  earth 
E,  also  by  a  thick  wire,  and  the  other  to  a  plate  or  elevated  conductor 
TV,  preferably  similar  to  u.  The  plate  w  may  be  suspended  on  a  pole 
x,  and  must  be  insulated  from  earth.  The  larger  the  plates  of  the 
receiver  and  transmitter,  and  the  higher  from  the  earth  the  plates  are 
carried  the  greater  is  the  distance  at  which  it  is  possible  to  communi- 
cate. When  using  the  last-described  apparatus,  it  is  not  necessary 
to  have  the  two  instruments  in  view  of  each  other,  as  it  is  of  no  con- 
sequence if  they  are  separated  by  mountains  or  other  obstacles.  At 
the  receiver  it  is  possible  to  pick  up  the  oscillations  from  the  earth  or 
water  without  having  the  plate  w.  This  may  be  done  by  connecting 
the  terminals  of  the  sensitive  tube  j  to  two  earths  preferably  at  a 
certain  distance  from  each  other  and  in  a  line  with  the  direction  from 
which  the  oscillations  are  coming.  These  connections  must  not  be 
entirely  conductive,  but  must  contain  a  condenser  of  suitable  capa- 
city—  say  one  square  yard  of  surface.  Balloons  can  also  be  used 
instead  of  plates  on  poles,  provided  they  carry  up  a  plate  or  are 
themselves  made  conductive  by  being  covered  with  tin-foil.  As  the 


212  APPENDIX    III. 

height  to  which  they  may  be  sent  is  great,  the  distance  at  which  com- 
munication is  possible  becomes  greatly  multiplied.  Kites  may  also 
be  successfully  employed,  if  made  conductive  by  means  of  tin-foil. 

The  apparatus  above  described  is  so  sensitive  that  it  is  essential 
either  that  the  transmitters  and  receivers  at  each  station  should  be  at 
a  considerable  distance  from  each  other  or  that  they  should  be 
screened  from  each  other  by  stout  metal  plates.  It  is  sufficient  to 
have  all  the  telegraphic  apparatus  in  a  metal  box  and  any  exposed 
part  of  the  circuit  of  the  receiver  inclosed  in  metallic  tubes  which  are 
in  electrical  communication  with  the  box.  Of  course  the  part  of  the 
apparatus  which  has  to  receive  the  radiation  from  the  distant  station 
must  not  be  inclosed,  but  possibly  screened  from  the  local  transmitter 
by  means  of  metallic  sheets.  When  working  through  the  earth  or 
water,  the  local  receiver  must  be  switched  out  of  circuit  when  the 
transmitter  is  at  work,  and  this  may  also  be  done  when  working 
through  air. 

The  operation  of  my  apparatus  and  system  of  communication  or 
signals  is  as  follows :  The  Ruhmkorff  coil  or  other  source  of  high 
tension  electrically  capable  of  producing  Hertz  oscillations  being  in 
circuit  with  a  signaling  instrument  —  such  as  a  Morse  key,  for 
instance  —  the  operator  by  closing  the  circuit  in  the  way  commonly 
employed  for  producing  dots  and  dashes  in  ordinary  telegraphy  will 
cause  the  oscillator  to  produce  either  a  short  or  a  more  prolonged 
electric  discharge  or  spark  or  succession  of  sparks,  and  this  will 
cause  a  corresponding  short  or  more  prolonged  oscillation  in  the  sur- 
rounding medium  corresponding  in  duration  to  the  short  or  longer 
electrical  impulse  which  in  ordinary  telegraphy  produces  a  dot  or 
dash.  Such  oscillations  of  defined  character  will  thereupon  be 
propagated  as  such  throughout  the  medium  and  will  affect  a  properly- 
constructed  instrument  at  a  distant  receiving-station.  At  such  sta- 
tion the  imperfect-contact  instrument  is  in  circuit  with  a  relay,  and 
when  oscillations  from  the  transmitting-station  reach  and  act  upon 
such  imperfect  contact  its  resistance  is  reduced,  and  the  circuit  is 
thereby  closed  during  the  continuance  of  the  oscillation  and  for  a 
length  of  time  corresponding  thereto.  The  closing  of  the  relay-cir- 
cuit causes  the  sounder  or  other  signal  apparatus  to  act  in  accord- 
ance with  the  particular  oscillation  received,  and  the  oscillation  also 
immediately  starts  the  action  of  the  shaking  or  tapping  device,  which 
so  shakes  the  powder  in  the  imperfect-contact  instrument  as  to  cause 
it  to  break  circuit  as  soon  as  the  oscillation  ceases  which  has  closed 
the  circuit  and  produced  a  movement  of  the  signaling  instrument 


APPENDIX    III,  213 

corresponding  thereto.  I  am  therefore  enabled  to  communicate  sig- 
nals telegraphically  without  wires  by  thus  artificially  forming  oscilla- 
tions at  the  transmitting-station  into  definite  signals  by  means  of  a 
signaling  instrument  and  receiving  and  reading  the  same  at  a  receiv- 
ing-station by  an  imperfect-contact  instrument,  which  when  acted 
upon  by  such  defined  oscillations  operates,  first,  to  close  the  circuit 
in  accordance  with  the  received  oscillation  and  produce  a  correspond- 
ing movement  of  the  receiving  instrument,  relay,  or  sounder,  and  also 
to  operate  a  shaking  device  to  automatically  reopen  the  circuit 
immediately  after  the  reception  of  each  oscillation,  thereby  preserv- 
ing the  results  of  its  defined  character  in  the  action  of  the  receiver. 

All  the  details  specified  herein  of  construction  of  the  sensitive 
tube  and  its  connections  are  desirable  for  great  efficiency ;  but  the 
fundamental  features  of  my  system  of  transmission  are  not  restricted 
to  such  details. 

I  am  aware  that  the  sensitiveness  of  various  apparatus,  including 
tubes  containing  filings,  to  more  or  less  distant  electrical  disturbances 
has  been  observed  in  a  general  way,  and  that  it  has  also  been  pro- 
posed to  disturb  the  conducting  of  such  filings  by  various  instru- 
mentalities for  shaking  the  tubes  containing  the  same.  I  am  also 
aware  that  the  use  of  tubes  containing  metallic  powders  of  several 
separate  kinds  has  been  described  or  suggested  in  connection  with 
certain  experiments  relating  to  so-called  "coherers,"  but  I  am  not 
aware  that  the  utility  of  a  mixture  of  metallic  powders  has  ever  previ- 
ous to  my  invention  been  ascertained  and  utilized  for  the  purpose  of 
obtaining  the  required  degree  of  sensitiveness  in  such  an  instrument. 

I  am  aware  of  the  publication  of  Professor  Lodge  of  1894,  at  Lon- 
don, England,  entitled  "The  Work  of  Hertz"  and  the  description, 
therein  of  various  instruments  in  connection  with  manifestations  of 
Hertz  oscillations.  I  am  also  aware  of  the  papers  by  Professor  Popoff 
in  the  Proceedings  of  the  Physical  and  Chemical  Society  of  Russia^ 
in  1895  or  1896 ;  but  in  neither  of  these  is  there  described  a  complete 
system  or  mechanism  capable  of  artificially  producing  Hertz  oscilla- 
tions and  forming  the  same  into  and  propagating  them  as  definite 
signals  and  capable  of  receiving  and  reproducing,  telegraphically,' 
such  definite  signals ;  nor  has  any  system  been  described,  to  my 
knowledge,  in  which  a  Hertz  oscillator  at  a  transmitting-station  and 
an  imperfect-contact  instrument  at  a  receiving-station  are  both 
arranged  with  one  terminal  to  earth  and  the  other  elevated  or  insu- 
lated ;  nor  am  I  aware  that  prior  to  my  invention  any  practical  form 
of  self-recovering  imperfect-contact  instrument  has  been  described. 


214  APPENDIX    III. 

I  believe  that  I  am  the  first  to  discover  and  use  any  practical 
means  for  effective  telegraphic  transmission  and  intelligible  recep- 
tion of  signals  produced  by  artificially-formed  Hertz  oscillations. 

What  I  claim  is  — 

1.  In  an  apparatus  for  communicating  electrical  signals  by  means 
of  a  producer  of  Hertz  oscillations  and  a  signaling  instrument,  the 
combination,  in  the  receiver,  of  an  imperfect  electrical  contact,  a  cir- 
cuit through  the  contact,  and  a  receiving  instrument  operated  by  the 
influence  of  such  oscillations  on  said   contact,  substantially  as  and 
for  the  purpose  described. 

2.  In  an  apparatus  for  communicating  electrical  signals  by  means 
of  a  producer  of  Hertz  oscillations  and  a  signaling  instrument,  the 
combination,  in  the  receiver,  of  an  imperfect  electrical  contact,  a  cir- 
cuit through  the  contact,  and  means,  controlled  by  said  circuit,  oper- 
ating to  shake  the   contact,  substantially  as   and  for  the  purpose 
described. 

3.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth  con- 
nection  to  one   end  of  the  spark-producer,  an  insulated  conductor 
connected  to  the  other  end,  an  imperfect  electrical  contact  at  the 
receiving-station,  an  earth  connection  to  one  end  of  the  contact,  an 
insulated  conductor  connected  to  the  other  end,  and  a  circuit  through 
the  contact,  substantially  as  and  for  the  purpose  described. 

4.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth  con- 
nection to  one  end  of   the  spark-producer,  an  insulated    conductor 
connected  to  the  other  end,  an  imperfect  electrical  contact  at  the 
receiving-station,  an  earth  connection  to  one  end  of  the  contact,  an 
insulated  conductor  connected  to  the  other  end,  a  circuit  through  the 
contact,  and  means,  controlled  by  the  circuit,  for  shaking  the  contact, 
substantially  as  and  for  the  purpose  described. 

5.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth  con- 
nection to  one  end  of  the  spark-producer,  an  insulated  conductor 
connected  to  the  other  end,  an  imperfect  electrical  contact  at  the 
i  receiving-station,  choking-coils  connected  to  each  end  of  the  contact, 
an  earth  connection  to  one  end  of  the  imperfect  contact,  an  insulated 
conductor  connected  to  the  other  end,  and  a  circuit  through  the  coils 
and  contact,  substantially  as  and  for  the  purpose  described. 

6.  The  combination,  in  an  apparatus  for  communicating  electri- 
cal signals  by  means  of  a  producer  of  Hertz  oscillations  and  a 


APPENDIX    III.  215 

signaling  instrument,  an  imperfect  electrical  contact  at  the  receiving- 
station,  choking-coils  connected  to  the  contact,  a  circuit  through 
the  coils  and  contact,  and  means,  controlled  by  the  circuit  and 
operating  to  shake  the  contact,  substantially  as  and  for  the  purpose 
described. 

7.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals  by  means  of  a  producer  of  Hertz  oscillations  and  a  signaling 
instrument,  an  imperfect  electrical  contact  at  the  receiving-station, 
means,  connected  to  each  end  of  the  contact,  to  prevent  the  oscilla- 
tion from  dissipating  itself,  a  circuit  through  said  means  and  contact, 
and  means,  controlled  by  the  circuit  and  operating  to  shake  the  con- 
tact, substantially  as  and  for  the  purpose  described. 

8.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth  con- 
nection to  one  end  of  the  spark-producer,  an  insulated  conductor  con- 
nected to  the  other  end,  a  tube  containing  metallic  powder  at  the 
receiving-station,  an  earth  connection  to  the  powder  and  an  insulated 
conductor  also  connected  therewith,  and  a  circuit  through  the  pow- 
der, substantially  as  and  for  the  purpose  described. 

9.  The  combination,  in  an  apparatus  for  communicating  electrical 
signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth  con- 
nection to  one  end  of  the  spark-producer,  an  insulated  conductor  con- 
nected to  the  other  end,  a  tube  containing  metallic  powder,  and  an 
insulated  conductor  also  connected  therewith,  a  circuit  through  the 
powder  and  means,  controlled  by  the  circuit,  for  shaking  the  powder, 
substantially  as  and  for  the  purpose  described. 

10.  The  combination,  in  an  apparatus  for  communicating  electri- 
cal signals,  of  a  spark-producer  at  the  transmitting-station,  an  earth 
connection  to  one  end  of  the  spark-producer,  an  insulated  conductor 
connected  to  the  other  end,  a  tube  containing  metallic  powder  at  the 
receiving-station,  choking-coils  connected    to   the   powder,  an   earth 
connection  to  the  powder  and  an  insulated  conductor  also  connected 
herewith,  and  a  circuit  through  the  coils  and  powder,  substantially 
as  and  for  the  purpose  described. 

n.  The  combination,  in  an  apparatus  for  communicating  electri- 
cal signals,  of  a  producer  of  Hertz  oscillations,  electrically  connected 
with  a  signaling  instrument  at  the  transmitting-station,  a  tube  con- 
taining metallic  powder  at  the  receiving-station,  choking-coils  con- 
nected to  the  powder,  a  circuit  through  the  powder,  and  means, 
controlled  by  said  circuit,  for  shaking  the  powder,  substantially  as 
and  for  the  purpose  described. 


2l6  APPENDIX   III. 

12.  The  combination,  in  an  apparatus  for  communicating  electri- 
cal signals,  of  a  producer  of  Hertz  oscillations,  electrically  connected 
with  a  signaling  instrument  at  the  transmitting-station,  a  tube  con- 
taining metallic  powder  at  the  receiving-station,  choking-coils  and 
earth  connection  through  condensers  connected  to  the  powder,  and 
means,  controlled  by  the  circuit,  for  shaking  the  powder,  substantially 
as  and  for  the  purpose  described. 

13.  The  combination,  in  an  apparatus  for  communicating  electri- 
cal signals,  of  a  producer  of  Hertz  oscillations,  electrically  connected 
with  a  signaling  instrument  at  the  transmitting-station,  a  tube  con- 
taining   metallic  powder  at  the  receiving-station,  electrically-tuned 
devices  connected  to  the  powder,  a  circuit  through  the  powder,  and 
means,  controlled  by  said  circuit,  for  shaking  the  powder,  substan- 
tially as  and  for  the  purpose  described. 

14.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  tuned  metallic  plates  connected  to  it,  a 
circuit  through  the  contact,  and  means,  controlled  by  the  circuit,  for 
shaking  the  contact. 

15.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  choking-coils  connected  to  the  contact,  a 
circuit  through  the  coils  and  contact,  and  means,  controlled  by  the 
circuit,  for  shaking  the  contact. 

16.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  tuned  metallic  plates  and  choking-coils 
connected  to  the  contact,  a  circuit  through  the  same,  and  means,  con- 
trolled by  the  circuit,  for  shaking  the  contact. 

17.  In  a  receiver  for  electrical  oscillations,  the  combination  of 
a  tube  containing  a  mixture  of  metallic  powders,  a  circuit  through 
the  same,   and  means,  controlled   by   the  circuit,   for  shaking   the 
powder. 

1 8.  In  a  receiver  for  electrical  oscillations,  the  combination  of  a 
tube  containing  a  metallic  powder  or  powders  and  mercury,  a  circuit 
through  the  same,  and  means,  controlled  by  the  circuit,  for  shaking 
the  powder. 

19.  In  a  receiver  for  electrical  oscillations,  the  combination  of  a 
tube,  metallic  plugs  in  the  tube,  metallic  powder  between  the  plugs, 
metallic  plates  connected  to  the  plugs,  choking-coils  connected  to  the 
plugs,  and  a  circuit  through  the  coils,  plugs,  and  powder. 

20.  In  a  receiver  for  electrical  oscillations,  the  combination  of  a 
tube,  metallic  plugs  in  the  tube,  metallic  powder  between  the  plugs, 
metallic  plates  connected  to  the  plugs,  choking-coils  connected  to  the 


APPENDIX   III.  217 

plugs,  a  circuit  through  the  coils,  plugs,  and  powder,  and  means, 
controlled  by  the  circuit,  for  shaking  the  powder. 

21.  In  a  receiver  for  electrical  oscillations,  the  combination  of  a 
tube,  metallic  plugs  in  the  tube,  a  mixture  of  metallic  powder  and 
mercury  between  the  plugs,  choking-coils  connected  to  the  plugs,  a 
circuit  through  the  coils,  plugs,  and  powder,  and  means,  controlled 
by  the  circuit,  for  shaking  the  powder. 

22.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  choking-coils  connected  to  the  contact, 
a  circuit  through  the  coils  and  contact,  a  relay  controlled  by  the  cir- 
cuit, and  means,  controlled  by  the  relay,  for  shaking  the  contact. 

23.  In  a  receiver  for  electrical  oscillations,  the  combination  of  an 
imperfect  electrical  contact,  a  circuit  through  the  contact,  an  electric 
trembler  shaking  the  contact,  and  means  for  preventing  the  self- 
induction  of  the  trembler  from  affecting  the  contact. 

24.  The  combination  of  a  transmitter  capable  of  producing  electri- 
cal oscillations  or  rays  of  definite  character  at  the  will  of  the  operator, 
and  a  receiver  located  at  a  distance  and  having  a  conductor  tuned  to  re- 
spond to  such  oscillations,  a  variable-resistance  medium  in  circuit  with 
the  conductor,  whose  resistance  is  altered  by  the  received  oscillations, 
means,  controlled  by  the  received  oscillations,  for  restoring  the  re- 
sistance medium  to  its  normal  condition  after  the  reception  of  such 
oscillations,  and  means  for  rendering  the  received  oscillations  mani- 
fest. 

In  witness  whereof  I  have  hereunto  signed  my  name,  at  18  Finch 
Lane,  in  the  city  of  London,  the  2gih  day  of  January,  in  the  year 
1901. 

GUGLIELMO   MARCONI. 

In  presence  of  — 

SAMUEL  FLOOD  PAGE, 
HUBERT  WILLOUGHBY  COREY. 


APPENDIX   IV. 


REPRESENTATIVE    CLAIMS    RELATING 
TO    WIRELESS   TRANSMISSION. 

FROM   THE    UNITED    STATES    PATENTS    OF   NIKOLA 

TESLAi    IN    CHRONOLOGICAL   ORDER 

OF    FILING   APPLICATIONS. 

U.  S.  Patent  No.  462,418,  Nov.  3,  1891;  filed  Feb.  4,  1891. 

1.  The   method  of  electrical   conversion   here  described,   which 
consists  in  discharging  a  condenser  or   conductor   possessing  capa- 
city and  maintaining  a  succession  of  intermittent  or  oscillating  dis- 
ruptive discharges  of  said  conductor  into  a  working  circuit  con- 
taining translating  devices. 

2.  In  a  system  of  electrical  conversion,  the  combination  of  a 
generator  or  source  of  electricity  and  a  line  or  generating  circuit 
containing  a  condenser  or  possessing  capacity,  and  a  working  cir- 
cuit operatively  connected  with  the  generating  circuit  through  one 
or  more  air-gaps  or  breaks  in  the  conducting  medium,  the  electri- 
cal conditions  being  so  adjusted  that  an  intermittent  or  oscillating 
disruptive  discharge  from  the  generating  into  the  working  circuit 
will  be  maintained,  as  set  forth. 

U.  S.  Patent  No.  454,622,  June  23,  1891 ;  filed  April  25,  1891. 

2.  The   method  of  producing  an  electric  current  for  practical 
application,  such  as  for  electric  lighting,  which  consists  in  gener- 
ating or  producing  a  current  of  enormous  frequency  and  inducing 
by  such  current  in  a  working  circuit,  or  that  to  which  the  light- 
ing devices  are  connected,  a  current  of  corresponding  frequency 
and  excessively  high  potential,  as  set  forth. 

3.  The  method  of  producing  an  electric  current  for  practical 

1  See  page  114. 
218 


APPENDIX    IV.  219 

application,  such  as  for  electric  lighting,  which  consists  in  charging 
a  condenser  by  a  given  current,  maintaining  an  intermittent  or 
oscillatory  discharge  of  said  condenser  through  or  into  a  primary 
circuit,  and  producing  thereby  in  a  secondary  working-circuit  in 
inductive  relation  to  the  primary  very  high  potentials,  as  set  forth. 

U.  S.  Patent  No.  568,176,  Sept.  22,  1896;  filed  April  22,  1896. 

1.  The  apparatus  herein  described  for  converting  direct  currents 
into  currents  of  high  frequency,  comprising  in  combination  a  cir- 
cuit of  high  self-induction,   a  circuit-controller  adapted  to   make 
and  break  such   circuit,  a  condenser  into  which  the  said  circuit 
discharges  when  interrupted,  and  a  transformer  through  the  pri- 
mary of  which  the  condenser  discharges  as  set  forth. 

2.  The  combination  of  a  source  of  direct  current  and  a  circuit 
therefrom,    choking-coils   in   said   circuit,   means   for   making   and 
breaking  the  circuit  through  said  coils,  a  condenser  around  the 
point  of  interruption  in  the  said  circuit  and  a  transformer  having 
its  primary  in  circuit  with  the  condenser  as  set  forth. 

3.  The  combination  with  a  circuit  of  high  self  induction   and 
means  for  making  and  breaking  the  same,  of  a  condenser  around 
the  point  of  interruption  in  the  said  circuit,  and  a  transformer  the 
primary  of  which  is  in  the  condenser-circuit  as  described. 

U.  S.  Patent  No.  568,178,  Sept,  22,  1896;  filed  June  20,  1896. 

1.  The  method  of  regulating  the  energy  delivered  by  a  system 
for  the  production  of  high  frequency  currents  and   comprising  a 
supply  circuit,  a  condenser,  a  circuit  through  which  the  same  dis- 
charges and  means  for  controlling  the  charging  of  the  condenser 
by  the  supply  circuit  and  the  discharging  of  the  same,  the  said 
method   consisting  in  varying  the  relations  of  the  frequencies  of 
the  impulses  in  the  circuits  comprising  the  system,  as  set  forth. 

2.  The  method  of  regulating  the  energy  delivered  by  a  system 
for  the  production  of  high  frequency  currents  comprising  a  supply- 
circuit  of  direct  currents,  a  condenser  adapted  to  be  charged  by 
the  supply-circuit  and  to  discharge  through  another  circuit,   the 
said  method  consisting  in  varying  the  frequency  of  the  impulses 
of  current  from  the  supply  circuit,  as  set  forth. 

3.  The  method  of  producing  and  regulating  electric  currents  of 
high  frequency  which  consists  in  directing  impulses  from  a  supply 
circuit  into  a  charging  circuit  of  high  self-induction,  charging  a 


220  APPENDIX    IV. 

condenser  by  the  accumulated  energy  of  such  charging  circuit, 
discharging  the  condenser  through  a  circuit  of  low  self-induction, 
raising  the  potential  of  the  condenser  discharge  and  varying  the 
relations  of  the  frequencies  of  the  electrical  impulses  in  the  said 
circuits,  as  herein  set  forth. 

U.  S.  Patent  No.  568,179,  Sept.  22,  1896;  filed  July  6,  1896. 

i.  The  method  herein  described  of  producing  electric  currents 
of  high  frequency,  which  consists  in  generating  an  alternating  cur- 
rent, charging  a  condenser  thereby  during  determinate  intervals  of 
each  wave  of  said  current,  and  discharging  the  condenser  through 
a  circuit  of  low  self-induction,  as  herein  set  forth. 

4.  The  combination  with  a  source  of  alternating  current,  a 
charging-circuit  in  which  the  energy  of  said  current  is  stored,  a 
circuit-controller  adapted  to  interrupt  the  charging-circuit  at  de- 
terminate points  in  each  wave,  a  condenser  for  receiving  on  the 
interruption  of  the  charging-circuit,  the  energy  accumulated  therein, 
and  a  circuit  into  which  the  condenser  discharges  when  connected 
therewith  by  the  circuit-controller,  as  set  forth. 

U.  S.  Patent  No.  568,180,  Sept.  22,  1896;  filed  July  9,  1896. 

i.  The  combination  with  a  source  of  current,  of  a  condenser 
adapted  to  be  charged  thereby,  a  circuit  into  which  the  condenser 
discharges  in  a  series  of  rapid  impulses,  and  a  circuit  controller 
for  effecting  the  charging  and  discharge  of  said  condenser,  com- 
posed of  conductors  movable  into  and  out  of  proximity  with  each 
other,  whereby  a  spark  may  be  maintained  between  them  and  the 
circuit  closed  thereby  during  determined  intervals,  as  set  forth. 

U.  S.  Patent  No.  577,670,  Feb.  23,  1897;  filed  Sept.  3,  1896. 

i.  The  combination  with  a  source  of  electric  energy,  of  a  plu- 
rality of  condensers  and  a  discharge  circuit  therefor,  a  motive  de- 
vice and  a  circuit-controller  operated  thereby  and  adapted  to 
direct  the  energy  of  the  source  into  the  condensers  and  connect 
them  with  the  discharge-circuit  successively  and  in  alternation,  as 
set  forth. 

U.  S.  Patent  No.  577,671,  Feb.  23,  1897;  filed  Nov.  5,  1896. 

i.  The  improvement  in  the  manufacture  of  electrical  devices 
such  as  condensers,  which  consists  in  inclosing  the  device  in  an 


APPENDIX    IV.  221 

air-tight  receptacle,  exhausting  the  air  from  the  receptacle,  intro- 
ducing into  a  vessel  containing  the  device  an  insulating  material 
rendered  fluid  by  heat,  and  then  when  said  material  has  perme- 
ated the  interstices  of  the  said  device,  subjecting  the  whole  to 
pressure,  and  maintaining  such  pressure  until  the  material  has 
cooled  and  solidified,  as  set  forth. 

U.  S.  Patent  No.  645,576,  March,  20,  1900;  filed  Sept.  2,  1897. 

2.  The  method  hereinbefore  described  of  transmitting  electrical 
energy,  which  consists  in  producing  at  a  generating  station  a  very 
high  electrical  pressure,  conducting  the  current  caused  thereby  to 
earth  and  to  a  terminal  at  an  elevation  at  which  the  atmosphere 
serves  as  a  conductor  therefor,   and  collecting  the  current  by  a 
second  elevated  terminal  at  a  distance  from  the  first. 

5.  The  method  hereinbefore  described  of  transmitting  electri- 
cal energy  through  the  natural  media,  which  consists  in  producing 
between  the  earth  and  a  generator-terminal  elevated  above  the 
same,  at  a  generating  station,  electrical  impulses  of  a  sufficiently- 
high  electromotive  force  to  render  elevated  air  strata  conducting, 
causing  thereby  current  impulses  to  pass,  by  conduction,  through 
the  air  strata,  and  collecting  or  receiving  at  a  point  distant  from  the 
generating  station,  the  energy  of  the  current  impulses  by  means  of 
a  circuit  synchronized  with  the  impulses. 

U.  S.  Patent  No.  649,621,  May  15,  1900;  filed  Sept.  2,  1897. 

3.  The  combination  with  a  transmitting  instrument  comprising 
a  transformer  having  its  secondary  connected  to  ground  and  to  an 
elevated  terminal  respectively,  and  means  for  impressing  electri- 
cal oscillations  upon  its  primary,  of  a  receiving  instrument  com- 
prising a  transformer  having  its  primary  similarly   connected  to 
ground  and  to  an  elevated  terminal,  and  a  translating  device  con- 
nected with  its  secondary,  the  capacity  and  inductance  of  the  two 
transformers  having  such  values  as  to  secure   synchronism   with 
the  impressed  oscillations,  as  set  forth. 

5.  The  combination  with  a  transmitting  coil  or  conductor  con- 
nected to  ground  and  an  elevated  terminal  respectively,  and  means 
for  producing  electrical  currents  or  oscillations  in  the  same,  of  a 
receiving  coil  or  conductor  similarly  connected  to  ground  and  to 
an  elevated  terminal  and  synchronized  with  the  transmitting  coil 
or  conductor,  as  set  forth. 


222  APPENDIX    IV. 

8.  The  combination  with  a  transmitting  coil  or  conductor  con- 
nected to  ground  and  to  an  elevated  terminal  respectively,  and 
adapted  to  cause  the   propagation  of  currents  or  oscillations  by 
conduction  through  the  natural  medium,  of  a  receiving-circuit  sim- 
ilarly connected  to  ground  and  to  an  elevated  terminal,  and  of  a 
capacity  and  inductance  such  that  its  period  of  vibration  is  the 
same  as  that  of  the  transmitter,  as  set  forth. 

9.  The  transmitting  or  receiving  circuit  herein  described,  con- 
nected to  ground  and  an  elevated  terminal  respectively,  and  ar- 
ranged in  such  manner  that  the  elevated  terminal  is  charged  to 
the  maximum  potential  developed  in  the  circuit,  as  set  forth. 

10.  The  combination  with  a  transmitting  coil  or  conductor  con- 
nected to  ground  and  to  an  elevated  terminal  respectively  of  a 
receiving-circuit  having  a  period  of  vibration  corresponding  to  that 
of  the  transmitting  circuit  and  similarly  connected  to  ground  and 
to  an  elevated  terminal  and  so  arranged  that  the  elevated  terminal 
is  charged  to  the  highest  potential  developed  in  the  circuit,  as  set 
forth. 

U.  S.  Patent  No.  611,719,  Oct.  4,  1898;  filed  Dec.  10,  1897. 

2.  The  combination  with  a  closed  receptacle,  of  a  circuit-con- 
troller contained  therein  and  means  for  maintaining  within  said 
receptacle  an  inert  atmosphere  under  pressure. 

4.  The  combination  with  a  circuit  controlling  mechanism,  one 
part  or  terminal  of  which  is  a  conducting  fluid,  such  as  mercury, 
of  a  receptacle  inclosing  the  same  and  means  for  maintaining  an 
inert  gas  under  pressure  in  the  receptacle. 

U.  S.  Patent  No.  613,809,  Nov.  8,  1898;  filed  July  i,  1898. 

7.  The  combination  with  a  source  of  electrical  waves  or  dis- 
turbances and  means  for  starting  and  stopping  the  same,  of  a  ves- 
sel or  vehicle,  propelling  and  steering  mechanism  carried  thereby, 
a  circuit  containing  or  connected  with  means  for  controlling  the 
operation  of  said  mechanism  and  adjusted  or  rendered  sensitive 
to  the  waves  or  disturbances  of  the  source,  as  set  forth. 

U.  S.  Patent  No.  685,953,  Nov.  5,  1901 ;  filed  June  24,  1899. 

2  The  method  of  transmitting  and  utilizing  electrical  energy 
herein  described,  which  consists  in  producing  electrical  disturb- 
ances or  effects  capable  of  being  transmitted  to  a  distance  through 


APPENDIX    IV.  223 

the  natural  media,  charging  a  condenser  at  a  distant  receiving 
station  with  energy  derived  from  such  effects  or  disturbances,  and 
using  for  periods  of  time,  predetermined  as  to  succession  and  dura- 
tion, the  potential  energy  so  obtained  to  operate  a  receiving  device. 
7.  The  method  herein  described  of  producing  arbitrarily  varied 
or  intermitted  electrical  disturbances  or  effects,  transmitting  such 
disturbances  or  effects  to  a  distant  receiving  station,  establishing 
thereby  a  flow  of  electrical  energy  in  a  circuit  at  such  station,  se- 
lecting or  directing  the  impulses  in  said  circuit  so  as  to  render 
them  suitable  for  charging  a  condenser,  charging  a  condenser  with 
the  impulses  so  selected  or  directed,  and  discharging  the  accumu- 
lated potential  energy  so  obtained  into,  or  through  a  receiving 
device. 

U.  S.  Patent  No.  685,954,  Nov.  5,  1901 ;  filed  Aug.  i,  1899. 

4.  The  method  hereinbefore  described  of  utilizing  effects  or  dis- 
turbances transmitted  through  the  natural  media,  which  consists 
in  controlling,  by  means  of  such  effects  or  disturbances,  the  charg- 
ing of  an  electrical  condenser  from  an  independent  source,  and 
discharging  the  stored  energy  through  a  receiving  circuit. 

U.  S.  Patent  No.  685,012,  Oct.  22,  1901;  filed  March  21,  1900. 

6.  In  a  system  for  the  transmission  of  energy,  a  series  of  trans- 
mitting and  receiving  circuits  adapted  to  vibrate  freely,  in  combi- 
nation with  means  for  artificially  maintaining  the  same  at  a  low 
temperature,  as  set  forth. 

U.  S.  Patent  725,605,  April  14,  1903;  filed  July  16,  1900. 

i.  In  a  system  for  the  transmission  of  electrical  energy,  the 
combination  with  means  for  producing  two  or  more  distinctive 
kinds  of  disturbances  or  impulses,  of  receiving  circuits,  each  tuned 
to  respond  to  the  waves  or  impulses  of  one  kind  only,  and  a  re- 
ceiving device  dependent  for  operation  upon  the  conjoint  action 
of  the  several  receiving  circuits,  as  set  forth. 

7.  The  combination   with  a   plurality  of  transmitter  elements, 
each  adapted  to  produce  a  series  of  impulses  or  disturbances  of  a 
distinctive  character,  and  means  for  controlling  and  adjusting  the 
same,  of  a  receiver  having  a   plurality  of  sensitive   circuits  each 
tuned  so  as  to  be  affected  by  one  of  the  series  of  impulses  only, 
and  dependent  for  operation  upon  the  conjoint  action  of  all  of  said 
circuits,  as  set  forth. 


224  APPENDIX   IV. 

8.  The  combination  with  a  transmitter  adapted  to  produce  a 
series  of  electrical  impulses  or  disturbances  of  distinctive  character 
and  in  a  given  order  of  succession,  of  a  receiving  apparatus  com- 
prising tuned  circuits  responding  to  such  impulses  in  a  correspond- 
ing order,  and  dependent  for  operation  upon  the  conjoint  action 
of  said  elements,  as  set  forth. 

12.  In  a  system  for  the  transmission  of  electrical  energy,  the 
combination   with   a   transmitting  apparatus  comprising  a   trans- 
former and  means  for  impressing  upon  the  secondary  element  of 
the  same  oscillations  or  impulses  of  different  character,  of  a  re- 
ceiving apparatus  comprising  a  plurality  of  circuits  each  tuned  to 
the  impulses  of  one  kind  emitted  by  the  secondary  of  the  trans- 
mitting transformer,  and  a  receiver  dependent  for  operation  upon 
the  conjoint  action  of  the  receiving  circuits,  as  set  forth. 

13.  In  a  system  for  the  transmission   of  electrical  energy,   the 
combination    with   a   transmitting   apparatus   comprising   a   trans- 
former and  means  for  impressing  upon  the  secondary  elements  of 
the  same  oscillations  or  impulses  of  different  periodicities  and  in 
a  given  order  of  succession,  of  a  receiving  apparatus  comprising  a 
plurality  of  circuits  each  tuned  to  respond  to  the  transmitted  im- 
pulses of  one  period,  and  a  receiver  dependent  for  operation  upon 
the  conjoint  action  of  the  receiving  circuits,  as  set  forth. 

16.  In  a  system  for  the  transmission  of  electrical  energy,  the 
combination  with  a  transmitter  adapted  to  produce  electrical  waves 
or  oscillations  varying  in  character  in  a  predetermined  order,  of  a 
receiving  instrument  responsive  to  said  oscillations  and  dependent 
for  operation  upon  the  action  thereof  in  a  corresponding  order,  as 
set  forth. 

U.  S.  Patent  723,188,  March  17,  1903;  filed  July  16,  1900. 

i.  The  method  of  operating  distant  receivers  which  consists  in 
producing  and  transmitting  a  plurality  of  kinds  or  classes  of  elec- 
trical impulses  or  disturbances,  actuating  by  the  impulses  or  dis- 
turbances of  each  kind  or  class  one  of  a  plurality  of  circuits  tuned 
to  respond  to  impulses  of  such  kind  or  class  and  operating  or  con- 
trolling the  operation  of  a  receiver  by  the  conjoint  action  of  two 
or  more  of  said  circuits,  as  set  forth. 

3.  The  method  of  signaling  which  consists  in  producing  a  plu- 
rality of  series  of  impulses  or  disturbances  differing  from  each 
other  in  character  and  order  of  succession,  exciting  by  the  im- 
pulses of  each  series  one  of  a  plurality  of  receiving-circuits  tuned 


APPENDIX    IV.  225 

to   respond   exclusively    thereto    and    controlling   by    the    conjoint 
action  of  such  circuits  a  local  circuit,  as  set  forth. 

9.  The  improvement  in  the  art  of  transmitting  electrical  energy 
which  consists  in  operating  or  controlling  a  receiving  mechanism 
by  a  series  or  group  of  electrical  impulses  of  different  periodici- 
ties and  of  a  predetermined  order  of  succession. 

U.  S.  Patent  No.  11,865;  a  reissue  Oct.  23,  1900.     Original  filed 
Aug.  14,  1900. 

i.  The  method  of  insulating  electric  conductors  herein  described 
which  consists  in  imparting  insulating  properties  to  material  sur- 
rounding or  contiguous  to  the  said  conductors  by  the  continued 
action  thereon  of  a  gaseous  cooling  agent,  as  set  forth. 

U.  S.  Patent  No.  685,958,  Nov.  5,  1901;  filed  March  21,  1901. 

i.  The  method  of  utilizing  radiant  energy,  which  consists  in 
charging  one  of  the  armatures  of  a  condenser  by  rays  or  radia- 
tions, and  the  other  armature  by  independent  means,  and  dis- 
charging the  condenser  through  a  suitable  receiver,  as  set  forth. 


NDEX. 


Achievement  (section  of  this  book), 
1 1. 

Anti-coherers,  154-157. 

Apparatus  (division  of  this  work) 
(Part  IV.),  143- 

Appendix,  190. 

Argentina  and  Italy,  Wireless  Com- 
munication between,  projected, 

22. 

Ayrton,  Professor,  Prophecy,  3. 

Barthelemy,  Abbe,  Prophetic  Writ 

ing,  2. 
Branly,  Prof. 

Hertzian-wave  coherer,  17,  153. 

Inventor  of  Filings  tube  Coherer, 

93-  98. 

Portrait,  opp.  91. 
Tripod  Coherer,  153. 

Cables,  Ocean. 

Cost,  128. 

Earnings,  127. 

Mileage,  gross,  128. 

Number,  128. 

Transmitting  speed,  128. 
Chemical     Telegraphy    (by    Wire), 
136. 

Description  and  Diagram,  137. 

Speed  of  Transmission,  138. 
Circuits,  Wireless  Telegraph,  26. 
Coherers. 

Descriptions,  152,  154. 


Collins,  A.  F.,  Wireless  Telephony, 

88. 

Comparative    Merits    of    Wire   and 
Space    Telegraphy    (a    division 
of   this  work),  125. 
Condensers. 

Description,  182. 

Function  in  Ruhmkorff  Coil,  147. 
Marconi's  Condenser,  183. 
Tesla's  Condenser,  183. 
Condensers,    Inductance    Coils    and 
Keys  (a  section  of  this  book),  182. 
Crookes,  Sir  William,  3. 

Davy,  Sir  Humphry,  4,  5. 
DeForest  System,  87. 
DeForest  Responder,  156,  157. 
DeForest  Transmitter,  149. 
Descriptive  (a  section  of  this  book), 

38. 

Discovery  (a  section  of  this  book),  4. 
Dolbear,  Prof.  Amos  E. 

Application  for  patent,  1882,  15. 

Mentioned,  96. 

U.S.  Patent  (in  full),  191. 

Edison,  Patent  of  1891,  96. 
Singing  Telephone,  13,  14. 
Signalling  to  moving  train,  1885, 

'5- 

Equipment,  Wireless,  Cost  of,  128. 
Explanatory  (a  section  of  this  book), 

24. 


226 


INDEX. 


227 


Faraday,  Michael,  4,  6. 
Feddersen  Experimentalist,  4,  7,  93. 
Fessenden,  Prof.  Reginald  A. 
Heat  Receiver,  166,  167. 
Interview  with,  69. 
Inventive  Record,  114-121. 
Prediction    of    Overland    Trans- 
mission, 130. 
Specialist    for    U.    S.    Weather 

Bureau,  66. 

Transmitters,  147-151. 
Wave-Responsive-Devices,      162- 

167. 

Wireless  Telegraph  Apparatus, 
Tests,  67. 

Gale,  L.  D.,  Experiments    for    Pro- 
fessor Morse,  12. 
Galileo's  prediction,  i,  2. 
Guarini,  Foresio. 

Suggestion  for  Multiplexing 
Ocean  Cables  with  Coherers, 
130. 

Wireless  Telegraph  Automatic 
Repeaters,  88,  130. 

Heat  Receiver,  Fessenden,  167. 
Henry,  Joseph,  4,  6,  7,  1 1. 
Helmholtz,  Hermann,  4,  6,  7. 
Hertz,  Heinrich. 

Anti-coherer,  154. 

Career  as  physicist,  8, 9. 

Crowning  achievement,  15. 

Discoveries,  97. 

Mentioned,  93. 

Portrait,  opp.  91. 

Pupil  of  Helmholtz,  4. 
Holy  Writ,  Quotation  from,  i. 
Huyghens,  Dutch  Philosopher, 

Originator  of  Undulatory  The- 
ory of  Light,  4,  5,  7. 


Hysteresis  defined,  164. 
Hysteresis,    Detector    of,    Marconi 
165. 

Inductance-Coils,  184. 

Inventors  and  inventions  (a  division 
of  this  book)  (Part  II.),  91. 

Inventions  in  Wireless  Telegraphy. 
Summary,  123. 

Italy  and  Argentina,  Wireless  Tele- 
graph projected  between,  22. 

Kelvin,  Lord,  Physicist,  4,  7. 
Keys,  Transmitting,  Fessenden  and 
Marconi,  186-189. 

Lesarge,  Pioneer  in  Electric  Teleg- 
raphy, ill 

Light,  Theories  of,  5,7. 
Localization  of  Wireless  Telegraph 
Signals,    33,    50,    74,    75,    117' 

223,  224. 

Lindsay,  James  Bowman,  2,  12,  13. 
Lodge,  Dr.  Oliver  Joseph. 
Biographical,  15. 
Discoverer,  4. 
Early  Experiments  with  Coherer, 


Patents,  99,  100,  101,  194. 
Portrait,  opp.  91. 
Signalling  Instrument  of  1 
System  Described,  63. 
System,  Diagram  of,  64. 


,  16. 


Magnetic  Radio  Receivers,  162,  166. 
Mail  Service,    Speed    of   Transmis- 

sion, 132. 
Marconi. 

Biographical,  18. 

Patents,  91,  101-113,  200-217. 
Maxwell,  James,  Clerk,  4-8,  93,  123. 

Portrait,  opp.  91. 
Methods,  Oldw.  New,  125. 


228 


INDEX. 


Micro  Radiophones,  157-162. 
Morse,  Prof.  S.  F.  B.,  n,  12. 
Muirhead,  Alexander,  3. 

Newton,  Sir  Isaac,  5. 
Nomenclature,  143. 
Non-tapping  Coherers. 

See      Micro      Radiophones     and 
Magnetic  Radio  Receivers. 

Onesti,  Calzecchi,  15,  97,  152. 
Overland  Transmission,  87. 

Patents,  Validity  of  Report  of  Com- 
missioner for  1892,  95. 
See  also  Dolbear,  Edison,  Ehret, 
Fessenden,      Lodge,      Marconi, 
Tesla. 

Poldhu   Station,    18-21,    176.       See 
also  Frontispiece. 

Pope,  Franklin  Leonard,  92,  93. 

Popoff,  Count,  17. 
Apparatus  of  April,  1 895.   Diagram 

and  Description,  93,  98,  99. 
Micro  Radiophone  of  1900,  157. 

Practicability,  Commercial,  of  Wire- 
less Telegraphy,  89. 

Preece,  Sir  Wm.  H.,  Early  Experi- 
ments in  Wireless  Telegraphy, 

H,  15- 

Prophecy  (section  of  this  book),  i. 
Pupin,  Dr.  M.  I.,  129,  131. 
Patents,  122. 

Resonance,  Electrical,  Theory,  27. 
Resonance,  Electrical,  Practice,  31. 
Responder,  DeForest,  155. 
Ruhmkorff  Coil,  Diagram  and  De 
scription,  145-147. 

Shields  for  Wireless  Telegraph  Re- 
ceivers, 179-181. 


Signals,  Telegraphic,  Illustration  of, 
Frontispiece  and  25. 

Slaby,  Dr.,  of  Germany,  56-62. 

Speeds  of  Signal  Propagation  by 
Wireless  and  by  Cables  Com- 
pared, 36. 

Steinheil,  Early  Telegrapher,  n. 

Strada,  Prophecy  of,  A.D.  1617,  2. 

Telegraph,  Electric,  Record  of,  n. 

Overland,  Cost  of,  128. 
Telephony,  Wireless,  74,  88. 
Terms,     in    Wireless     Telegraphy. 

See  Nomenclature. 
Tesla. 

Biographical,  38. 

Concatenated  Tuned  Circuits,  48. 
Conversion,    Electrical,    by   Con- 
denser Discharges,  45. 
Filings,  Tube  Coherer,  153. 
Long     Distance     Power     Trans- 
mission, 38-43. 
Long  Island  Plant,  opp.  49. 
Mentioned,  4. 

Patent  Claims,  114,  218-225. 
Portrait,  opp.  43. 
Prediction  of  1893,  3. 
Telautomata,  44. 
Transmitter   of    High  Potentials, 

42. 

Sun  Motors,  53. 

Transmission  (Transatlantic),  Fron- 
tispiece and  1 8-2 1. 
Transmission  (Wireless),  not  affect- 
ed by  distance,  128. 
Tuning  (Electrical),  27. 

(See  also  Resonance.) 
Tuned  Circuits,  48. 

United  States  Government. 
Wireless  Stations,  66. 


INDEX. 


229 


Practice  Tests,  67. 
Proposals     for     Wireless      Tele- 
graphs, 68. 
Work  of  Weather  Bureau,  66. 

Wave-Gates  (section  of  this  book), 

1 68. 
Wave- Responsive-Devices    (section 

of  this  book),  152. 


Western  Union  Telegraph  Com 
pany's  Controversy  with  Dr. 
Pupin,  131. 

Wire  Telegraphy. 
Types  and  Apparatus,  133. 

Young,  Dr.  Thomas,  5. 


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WORMELL,  R.  Electricity  in  the  Service  of  Man.  A  Popular  and  Practical 
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